Move 650 lines of gr-diff css into its own file

gr-diff has more than 1,000 lines even witout the css. Let's move the
css into its own file. Ultimately we want to break up the css into
smaller pieces and move it where it is relevant. But that is for later.

Release-Notes: skip
Change-Id: I0704357805e539c0c19334059afc096b3f7e72b3
(cherry picked from commit 5777ae5c95c1e8f3dae77676e4432a17516e0d71)
diff --git a/polygerrit-ui/app/embed/diff/gr-diff/gr-diff-styles.ts b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff-styles.ts
new file mode 100644
index 0000000..e7f4b51
--- /dev/null
+++ b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff-styles.ts
@@ -0,0 +1,671 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import {css} from 'lit';
+
+export const grDiffStyles = css`
+  /* This is used to hide all left side of the diff (e.g. diffs besides
+     comments in the change log). Since we want to remove the first 4
+     cells consistently in all rows except context buttons (.dividerRow). */
+  :host(.no-left) .sideBySide colgroup col:nth-child(-n + 4),
+  :host(.no-left) .sideBySide tr:not(.dividerRow) td:nth-child(-n + 4) {
+    display: none;
+  }
+  :host(.disable-context-control-buttons) {
+    --context-control-display: none;
+  }
+  :host(.disable-context-control-buttons) .section {
+    border-right: none;
+  }
+  :host(.hide-line-length-indicator) .full-width td.content .contentText {
+    background-image: none;
+  }
+
+  :host {
+    font-family: var(--monospace-font-family, ''), 'Roboto Mono';
+    font-size: var(--font-size, var(--font-size-code, 12px));
+    /* usually 16px = 12px + 4px */
+    line-height: calc(
+      var(--font-size, var(--font-size-code, 12px)) + var(--spacing-s, 4px)
+    );
+  }
+
+  .thread-group {
+    display: block;
+    max-width: var(--content-width, 80ch);
+    white-space: normal;
+    background-color: var(--diff-blank-background-color);
+  }
+  .diffContainer {
+    max-width: var(--diff-max-width, none);
+    font-family: var(--monospace-font-family);
+  }
+  table {
+    border-collapse: collapse;
+    table-layout: fixed;
+  }
+  td.lineNum {
+    /* Enforces background whenever lines wrap */
+    background-color: var(--diff-blank-background-color);
+  }
+
+  /* Provides the option to add side borders (left and right) to the line
+     number column. */
+  td.lineNum,
+  td.blankLineNum,
+  td.moveControlsLineNumCol,
+  td.contextLineNum {
+    box-shadow: var(--line-number-box-shadow, unset);
+  }
+
+  /* Context controls break up the table visually, so we set the right
+     border on individual sections to leave a gap for the divider.
+
+     Also taken into account for max-width calculations in SHRINK_ONLY mode
+     (check GrDiff.updatePreferenceStyles). */
+  .section {
+    border-right: 1px solid var(--border-color);
+  }
+  .section.contextControl {
+    /* Divider inside this section must not have border; we set borders on
+       the padding rows below. */
+    border-right-width: 0;
+  }
+  /* Padding rows behind context controls. The diff is styled to be cut
+     into two halves by the negative space of the divider on which the
+     context control buttons are anchored. */
+  .contextBackground {
+    border-right: 1px solid var(--border-color);
+  }
+  .contextBackground.above {
+    border-bottom: 1px solid var(--border-color);
+  }
+  .contextBackground.below {
+    border-top: 1px solid var(--border-color);
+  }
+
+  .lineNumButton {
+    display: block;
+    width: 100%;
+    height: 100%;
+    background-color: var(--diff-blank-background-color);
+    box-shadow: var(--line-number-box-shadow, unset);
+  }
+  td.lineNum {
+    vertical-align: top;
+  }
+
+  /* The only way to focus this (clicking) will apply our own focus
+     styling, so this default styling is not needed and distracting. */
+  .lineNumButton:focus {
+    outline: none;
+  }
+  gr-image-viewer {
+    width: 100%;
+    height: 100%;
+    max-width: var(--image-viewer-max-width, 95vw);
+    max-height: var(--image-viewer-max-height, 90vh);
+    /* Defined by paper-styles default-theme and used in various
+       components. background-color-secondary is a compromise between
+       fairly light in light theme (where we ideally would want
+       background-color-primary) yet slightly offset against the app
+       background in dark mode, where drop shadows e.g. around paper-card
+       are almost invisible. */
+    --primary-background-color: var(--background-color-secondary);
+  }
+  .image-diff .gr-diff {
+    text-align: center;
+  }
+  .image-diff img {
+    box-shadow: var(--elevation-level-1);
+    max-width: 50em;
+  }
+  .image-diff .right.lineNumButton {
+    border-left: 1px solid var(--border-color);
+  }
+  .image-diff label {
+    font-family: var(--font-family);
+    font-style: italic;
+  }
+  tbody.binary-diff td {
+    font-family: var(--font-family);
+    font-style: italic;
+    text-align: center;
+    padding: var(--spacing-s) 0;
+  }
+  .diff-row {
+    outline: none;
+    user-select: none;
+  }
+  .diff-row.target-row.target-side-left .lineNumButton.left,
+  .diff-row.target-row.target-side-right .lineNumButton.right,
+  .diff-row.target-row.unified .lineNumButton {
+    color: var(--primary-text-color);
+  }
+
+  /* Preparing selected line cells with position relative so it allows a
+     positioned overlay with 'position: absolute'. */
+  .target-row td {
+    position: relative;
+  }
+
+  /* Defines an overlay to the selected line for drawing an outline without
+     blocking user interaction (e.g. text selection). */
+  .target-row td::before {
+    border-width: 0;
+    border-style: solid;
+    border-color: var(--focused-line-outline-color);
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    pointer-events: none;
+    user-select: none;
+    content: ' ';
+  }
+
+  /* The outline for the selected content cell should be the same in all
+     cases. */
+  .target-row.target-side-left td.left.content::before,
+  .target-row.target-side-right td.right.content::before,
+  .unified.target-row td.content::before {
+    border-width: 1px 1px 1px 0;
+  }
+
+  /* The outline for the sign cell should be always be contiguous
+     top/bottom. */
+  .target-row.target-side-left td.left.sign::before,
+  .target-row.target-side-right td.right.sign::before {
+    border-width: 1px 0;
+  }
+
+  /* For side-by-side we need to select the correct line number to
+     "visually close" the outline. */
+  .side-by-side.target-row.target-side-left td.left.lineNum::before,
+  .side-by-side.target-row.target-side-right td.right.lineNum::before {
+    border-width: 1px 0 1px 1px;
+  }
+
+  /* For unified diff we always start the overlay from the left cell. */
+  .unified.target-row td.left:not(.content)::before {
+    border-width: 1px 0 1px 1px;
+  }
+
+  /* For unified diff we should continue the top/bottom border in right
+     line number column. */
+  .unified.target-row td.right:not(.content)::before {
+    border-width: 1px 0;
+  }
+
+  .content {
+    background-color: var(--diff-blank-background-color);
+  }
+
+  /* Describes two states of semantic tokens: whenever a token has a
+     definition that can be navigated to (navigable) and whenever
+     the token is actually clickable to perform this navigation. */
+  .semantic-token.navigable {
+    text-decoration-style: dotted;
+    text-decoration-line: underline;
+  }
+  .semantic-token.navigable.clickable {
+    text-decoration-style: solid;
+    cursor: pointer;
+  }
+
+  /* The file line, which has no contentText, add some margin before the
+     first comment. We cannot add padding the container because we only
+     want it if there is at least one comment thread, and the slotting
+     makes :empty not work as expected. */
+  .content.file slot:first-child::slotted(.comment-thread) {
+    display: block;
+    margin-top: var(--spacing-xs);
+  }
+  .contentText {
+    background-color: var(--view-background-color);
+  }
+  .blank {
+    background-color: var(--diff-blank-background-color);
+  }
+  .image-diff .content {
+    background-color: var(--diff-blank-background-color);
+  }
+  .responsive {
+    width: 100%;
+  }
+  .responsive .contentText {
+    white-space: break-spaces;
+    word-break: break-all;
+  }
+  .lineNumButton,
+  .content {
+    vertical-align: top;
+    white-space: pre;
+  }
+  .contextLineNum,
+  .lineNumButton {
+    -webkit-user-select: none;
+    -moz-user-select: none;
+    -ms-user-select: none;
+    user-select: none;
+
+    color: var(--deemphasized-text-color);
+    padding: 0 var(--spacing-m);
+    text-align: right;
+  }
+  .canComment .lineNumButton {
+    cursor: pointer;
+  }
+  .sign {
+    min-width: 1ch;
+    width: 1ch;
+    background-color: var(--view-background-color);
+  }
+  .sign.blank {
+    background-color: var(--diff-blank-background-color);
+  }
+  .content {
+    /* Set min width since setting width on table cells still allows them
+       to shrink. Do not set max width because CJK
+       (Chinese-Japanese-Korean) glyphs have variable width. */
+    min-width: var(--content-width, 80ch);
+    width: var(--content-width, 80ch);
+  }
+  /* If there are no intraline info, consider everything changed */
+  .content.add .contentText .intraline,
+  .content.add.no-intraline-info .contentText,
+  .sign.add.no-intraline-info,
+  .delta.total .content.add .contentText {
+    background-color: var(--dark-add-highlight-color);
+  }
+  .content.add .contentText,
+  .sign.add {
+    background-color: var(--light-add-highlight-color);
+  }
+  /* If there are no intraline info, consider everything changed */
+  .content.remove .contentText .intraline,
+  .content.remove.no-intraline-info .contentText,
+  .delta.total .content.remove .contentText,
+  .sign.remove.no-intraline-info {
+    background-color: var(--dark-remove-highlight-color);
+  }
+  .content.remove .contentText,
+  .sign.remove {
+    background-color: var(--light-remove-highlight-color);
+  }
+
+  .ignoredWhitespaceOnly .sign.no-intraline-info {
+    background-color: var(--view-background-color);
+  }
+
+  /* dueToRebase */
+  .dueToRebase .content.add .contentText .intraline,
+  .delta.total.dueToRebase .content.add .contentText {
+    background-color: var(--dark-rebased-add-highlight-color);
+  }
+  .dueToRebase .content.add .contentText {
+    background-color: var(--light-rebased-add-highlight-color);
+  }
+  .dueToRebase .content.remove .contentText .intraline,
+  .delta.total.dueToRebase .content.remove .contentText {
+    background-color: var(--dark-rebased-remove-highlight-color);
+  }
+  .dueToRebase .content.remove .contentText {
+    background-color: var(--light-rebased-remove-highlight-color);
+  }
+
+  /* dueToMove */
+  .dueToMove .sign.add,
+  .dueToMove .content.add .contentText,
+  .dueToMove .moveControls.movedIn .sign.right,
+  .dueToMove .moveControls.movedIn .moveHeader,
+  .delta.total.dueToMove .content.add .contentText {
+    background-color: var(--diff-moved-in-background);
+  }
+
+  .dueToMove.changed .sign.add,
+  .dueToMove.changed .content.add .contentText,
+  .dueToMove.changed .moveControls.movedIn .sign.right,
+  .dueToMove.changed .moveControls.movedIn .moveHeader,
+  .delta.total.dueToMove.changed .content.add .contentText {
+    background-color: var(--diff-moved-in-changed-background);
+  }
+
+  .dueToMove .sign.remove,
+  .dueToMove .content.remove .contentText,
+  .dueToMove .moveControls.movedOut .moveHeader,
+  .dueToMove .moveControls.movedOut .sign.left,
+  .delta.total.dueToMove .content.remove .contentText {
+    background-color: var(--diff-moved-out-background);
+  }
+
+  .delta.dueToMove .movedIn .moveHeader {
+    --gr-range-header-color: var(--diff-moved-in-label-color);
+  }
+  .delta.dueToMove.changed .movedIn .moveHeader {
+    --gr-range-header-color: var(--diff-moved-in-changed-label-color);
+  }
+  .delta.dueToMove .movedOut .moveHeader {
+    --gr-range-header-color: var(--diff-moved-out-label-color);
+  }
+
+  .moveHeader a {
+    color: inherit;
+  }
+
+  /* ignoredWhitespaceOnly */
+  .ignoredWhitespaceOnly .content.add .contentText .intraline,
+  .delta.total.ignoredWhitespaceOnly .content.add .contentText,
+  .ignoredWhitespaceOnly .content.add .contentText,
+  .ignoredWhitespaceOnly .content.remove .contentText .intraline,
+  .delta.total.ignoredWhitespaceOnly .content.remove .contentText,
+  .ignoredWhitespaceOnly .content.remove .contentText {
+    background-color: var(--view-background-color);
+  }
+
+  .content .contentText gr-diff-text:empty:after,
+  .content .contentText gr-legacy-text:empty:after,
+  .content .contentText:empty:after {
+    /* Newline, to ensure empty lines are one line-height tall. */
+    content: '\\A';
+  }
+
+  /* Context controls */
+  .contextControl {
+    display: var(--context-control-display, table-row-group);
+    background-color: transparent;
+    border: none;
+    --divider-height: var(--spacing-s);
+    --divider-border: 1px;
+  }
+  /* TODO: Is this still used? */
+  .contextControl gr-button gr-icon {
+    /* should match line-height of gr-button */
+    font-size: var(--line-height-mono, 18px);
+  }
+  .contextControl td:not(.lineNumButton) {
+    text-align: center;
+  }
+
+  /* Padding rows behind context controls. Styled as a continuation of the
+     line gutters and code area. */
+  .contextBackground > .contextLineNum {
+    background-color: var(--diff-blank-background-color);
+  }
+  .contextBackground > td:not(.contextLineNum) {
+    background-color: var(--view-background-color);
+  }
+  .contextBackground {
+    /* One line of background behind the context expanders which they can
+       render on top of, plus some padding. */
+    height: calc(var(--line-height-normal) + var(--spacing-s));
+  }
+
+  .dividerCell {
+    vertical-align: top;
+  }
+  .dividerRow.show-both .dividerCell {
+    height: var(--divider-height);
+  }
+  .dividerRow.show-above .dividerCell,
+  .dividerRow.show-above .dividerCell {
+    height: 0;
+  }
+
+  .br:after {
+    /* Line feed */
+    content: '\\A';
+  }
+  .tab {
+    display: inline-block;
+  }
+  .tab-indicator:before {
+    color: var(--diff-tab-indicator-color);
+    /* >> character */
+    content: '\\00BB';
+    position: absolute;
+  }
+  .special-char-indicator {
+    /* spacing so elements don't collide */
+    padding-right: var(--spacing-m);
+  }
+  .special-char-indicator:before {
+    color: var(--diff-tab-indicator-color);
+    content: '•';
+    position: absolute;
+  }
+  .special-char-warning {
+    /* spacing so elements don't collide */
+    padding-right: var(--spacing-m);
+  }
+  .special-char-warning:before {
+    color: var(--warning-foreground);
+    content: '!';
+    position: absolute;
+  }
+  /* Is defined after other background-colors, such that this
+     rule wins in case of same specificity. */
+  .trailing-whitespace,
+  .content .contentText .trailing-whitespace,
+  .trailing-whitespace .intraline,
+  .content .contentText .trailing-whitespace .intraline {
+    border-radius: var(--border-radius, 4px);
+    background-color: var(--diff-trailing-whitespace-indicator);
+  }
+  #diffHeader {
+    background-color: var(--table-header-background-color);
+    border-bottom: 1px solid var(--border-color);
+    color: var(--link-color);
+    padding: var(--spacing-m) 0 var(--spacing-m) 48px;
+  }
+  #diffTable {
+    /* for gr-selection-action-box positioning */
+    position: relative;
+  }
+  #diffTable:focus {
+    outline: none;
+  }
+  #loadingError,
+  #sizeWarning {
+    display: block;
+    margin: var(--spacing-l) auto;
+    max-width: 60em;
+    text-align: center;
+  }
+  #loadingError {
+    color: var(--error-text-color);
+  }
+  #sizeWarning gr-button {
+    margin: var(--spacing-l);
+  }
+  .target-row td.blame {
+    background: var(--diff-selection-background-color);
+  }
+  td.lost div {
+    background-color: var(--info-background);
+  }
+  td.lost div.lost-message {
+    font-family: var(--font-family, 'Roboto');
+    font-size: var(--font-size-normal, 14px);
+    line-height: var(--line-height-normal);
+    padding: var(--spacing-s) 0;
+  }
+  td.lost div.lost-message gr-icon {
+    padding: 0 var(--spacing-s) 0 var(--spacing-m);
+    color: var(--blue-700);
+  }
+
+  col.sign,
+  td.sign {
+    display: none;
+  }
+
+  /* Sign column should only be shown in high-contrast mode. */
+  :host(.with-sign-col) col.sign {
+    display: table-column;
+  }
+  :host(.with-sign-col) td.sign {
+    display: table-cell;
+  }
+  col.blame {
+    display: none;
+  }
+  td.blame {
+    display: none;
+    padding: 0 var(--spacing-m);
+    white-space: pre;
+  }
+  :host(.showBlame) col.blame {
+    display: table-column;
+  }
+  :host(.showBlame) td.blame {
+    display: table-cell;
+  }
+  td.blame > span {
+    opacity: 0.6;
+  }
+  td.blame > span.startOfRange {
+    opacity: 1;
+  }
+  td.blame .blameDate {
+    font-family: var(--monospace-font-family);
+    color: var(--link-color);
+    text-decoration: none;
+  }
+  .responsive td.blame {
+    overflow: hidden;
+    width: 200px;
+  }
+  /** Support the line length indicator **/
+  .responsive td.content .contentText {
+    /* Same strategy as in
+       https://stackoverflow.com/questions/1179928/how-can-i-put-a-vertical-line-down-the-center-of-a-div
+       */
+    background-image: linear-gradient(
+      var(--line-length-indicator-color),
+      var(--line-length-indicator-color)
+    );
+    background-size: 1px 100%;
+    background-position: var(--line-limit-marker) 0;
+    background-repeat: no-repeat;
+  }
+  .newlineWarning {
+    color: var(--deemphasized-text-color);
+    text-align: center;
+  }
+  .newlineWarning.hidden {
+    display: none;
+  }
+  .lineNum.COVERED .lineNumButton {
+    color: var(
+      --coverage-covered-line-num-color,
+      var(--deemphasized-text-color)
+    );
+    background-color: var(--coverage-covered, #e0f2f1);
+  }
+  .lineNum.NOT_COVERED .lineNumButton {
+    color: var(
+      --coverage-covered-line-num-color,
+      var(--deemphasized-text-color)
+    );
+    background-color: var(--coverage-not-covered, #ffd1a4);
+  }
+  .lineNum.PARTIALLY_COVERED .lineNumButton {
+    color: var(
+      --coverage-covered-line-num-color,
+      var(--deemphasized-text-color)
+    );
+    background: linear-gradient(
+      to right bottom,
+      var(--coverage-not-covered, #ffd1a4) 0%,
+      var(--coverage-not-covered, #ffd1a4) 50%,
+      var(--coverage-covered, #e0f2f1) 50%,
+      var(--coverage-covered, #e0f2f1) 100%
+    );
+  }
+
+  // TODO: Investigate whether this CSS is still necessary.
+  /* BEGIN: Select and copy for Polymer 2 */
+  /* Below was copied and modified from the original css in gr-diff-selection.html. */
+  .content,
+  .contextControl,
+  .blame {
+    -webkit-user-select: none;
+    -moz-user-select: none;
+    -ms-user-select: none;
+    user-select: none;
+  }
+
+  .selected-left:not(.selected-comment)
+    .side-by-side
+    .left
+    + .content
+    .contentText,
+  .selected-right:not(.selected-comment)
+    .side-by-side
+    .right
+    + .content
+    .contentText,
+  .selected-left:not(.selected-comment)
+    .unified
+    .left.lineNum
+    ~ .content:not(.both)
+    .contentText,
+  .selected-right:not(.selected-comment)
+    .unified
+    .right.lineNum
+    ~ .content
+    .contentText,
+  .selected-left.selected-comment .side-by-side .left + .content .message,
+  .selected-right.selected-comment
+    .side-by-side
+    .right
+    + .content
+    .message
+    :not(.collapsedContent),
+  .selected-comment .unified .message :not(.collapsedContent),
+  .selected-blame .blame {
+    -webkit-user-select: text;
+    -moz-user-select: text;
+    -ms-user-select: text;
+    user-select: text;
+  }
+
+  /* Make comments and check results selectable when selected */
+  .selected-left.selected-comment ::slotted(.comment-thread[diff-side='left']),
+  .selected-right.selected-comment
+    ::slotted(.comment-thread[diff-side='right']) {
+    -webkit-user-select: text;
+    -moz-user-select: text;
+    -ms-user-select: text;
+    user-select: text;
+  }
+  /* END: Select and copy for Polymer 2 */
+
+  .whitespace-change-only-message {
+    background-color: var(--diff-context-control-background-color);
+    border: 1px solid var(--diff-context-control-border-color);
+    text-align: center;
+  }
+
+  .token-highlight {
+    background-color: var(--token-highlighting-color, #fffd54);
+  }
+
+  gr-selection-action-box {
+    /* Needs z-index to appear above wrapped content, since it's inserted
+       into DOM before it. */
+    z-index: 10;
+  }
+
+  gr-diff-image-new,
+  gr-diff-image-old,
+  gr-diff-section,
+  gr-context-controls-section,
+  gr-diff-row {
+    display: contents;
+  }
+`;
diff --git a/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts
index 3d54690..3929330 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts
@@ -65,7 +65,7 @@
 import {GrDiffSelection} from '../gr-diff-selection/gr-diff-selection';
 import {customElement, property, query, state} from 'lit/decorators.js';
 import {sharedStyles} from '../../../styles/shared-styles';
-import {css, html, LitElement, nothing, PropertyValues} from 'lit';
+import {html, LitElement, nothing, PropertyValues} from 'lit';
 import {when} from 'lit/directives/when.js';
 import {grSyntaxTheme} from '../gr-syntax-themes/gr-syntax-theme';
 import {grRangedCommentTheme} from '../gr-ranged-comment-themes/gr-ranged-comment-theme';
@@ -74,6 +74,7 @@
 import {expandFileMode} from '../../../utils/file-util';
 import {DiffModel, diffModelToken} from '../gr-diff-model/gr-diff-model';
 import {provide} from '../../../models/dependency';
+import {grDiffStyles} from './gr-diff-styles';
 
 const NO_NEWLINE_LEFT = 'No newline at end of left file.';
 const NO_NEWLINE_RIGHT = 'No newline at end of right file.';
@@ -278,718 +279,7 @@
       sharedStyles,
       grSyntaxTheme,
       grRangedCommentTheme,
-      css`
-        /**
-          This is used to hide all left side of the diff (e.g. diffs besides
-          comments in the change log). Since we want to remove the first 4
-          cells consistently in all rows except context buttons (.dividerRow).
-        */
-        :host(.no-left) .sideBySide colgroup col:nth-child(-n + 4),
-        :host(.no-left) .sideBySide tr:not(.dividerRow) td:nth-child(-n + 4) {
-          display: none;
-        }
-        :host(.disable-context-control-buttons) {
-          --context-control-display: none;
-        }
-        :host(.disable-context-control-buttons) .section {
-          border-right: none;
-        }
-        :host(.hide-line-length-indicator) .full-width td.content .contentText {
-          background-image: none;
-        }
-
-        :host {
-          font-family: var(--monospace-font-family, ''), 'Roboto Mono';
-          font-size: var(--font-size, var(--font-size-code, 12px));
-          /* usually 16px = 12px + 4px */
-          line-height: calc(
-            var(--font-size, var(--font-size-code, 12px)) +
-              var(--spacing-s, 4px)
-          );
-        }
-
-        .thread-group {
-          display: block;
-          max-width: var(--content-width, 80ch);
-          white-space: normal;
-          background-color: var(--diff-blank-background-color);
-        }
-        .diffContainer {
-          max-width: var(--diff-max-width, none);
-          font-family: var(--monospace-font-family);
-        }
-        table {
-          border-collapse: collapse;
-          table-layout: fixed;
-        }
-        td.lineNum {
-          /* Enforces background whenever lines wrap */
-          background-color: var(--diff-blank-background-color);
-        }
-
-        /**
-          Provides the option to add side borders (left and right) to the line
-          number column.
-        */
-        td.lineNum,
-        td.blankLineNum,
-        td.moveControlsLineNumCol,
-        td.contextLineNum {
-          box-shadow: var(--line-number-box-shadow, unset);
-        }
-
-        /**
-          Context controls break up the table visually, so we set the right
-          border on individual sections to leave a gap for the divider.
-
-          Also taken into account for max-width calculations in SHRINK_ONLY mode
-          (check GrDiff.updatePreferenceStyles).
-        */
-        .section {
-          border-right: 1px solid var(--border-color);
-        }
-        .section.contextControl {
-          /**
-            Divider inside this section must not have border; we set borders on
-            the padding rows below.
-          */
-          border-right-width: 0;
-        }
-        /**
-          Padding rows behind context controls. The diff is styled to be cut
-          into two halves by the negative space of the divider on which the
-          context control buttons are anchored.
-        */
-        .contextBackground {
-          border-right: 1px solid var(--border-color);
-        }
-        .contextBackground.above {
-          border-bottom: 1px solid var(--border-color);
-        }
-        .contextBackground.below {
-          border-top: 1px solid var(--border-color);
-        }
-
-        .lineNumButton {
-          display: block;
-          width: 100%;
-          height: 100%;
-          background-color: var(--diff-blank-background-color);
-          box-shadow: var(--line-number-box-shadow, unset);
-        }
-        td.lineNum {
-          vertical-align: top;
-        }
-
-        /**
-          The only way to focus this (clicking) will apply our own focus
-          styling, so this default styling is not needed and distracting.
-        */
-        .lineNumButton:focus {
-          outline: none;
-        }
-        gr-image-viewer {
-          width: 100%;
-          height: 100%;
-          max-width: var(--image-viewer-max-width, 95vw);
-          max-height: var(--image-viewer-max-height, 90vh);
-          /**
-            Defined by paper-styles default-theme and used in various
-            components. background-color-secondary is a compromise between
-            fairly light in light theme (where we ideally would want
-            background-color-primary) yet slightly offset against the app
-            background in dark mode, where drop shadows e.g. around paper-card
-            are almost invisible.
-          */
-          --primary-background-color: var(--background-color-secondary);
-        }
-        .image-diff .gr-diff {
-          text-align: center;
-        }
-        .image-diff img {
-          box-shadow: var(--elevation-level-1);
-          max-width: 50em;
-        }
-        .image-diff .right.lineNumButton {
-          border-left: 1px solid var(--border-color);
-        }
-        .image-diff label {
-          font-family: var(--font-family);
-          font-style: italic;
-        }
-        tbody.binary-diff td {
-          font-family: var(--font-family);
-          font-style: italic;
-          text-align: center;
-          padding: var(--spacing-s) 0;
-        }
-        .diff-row {
-          outline: none;
-          user-select: none;
-        }
-        .diff-row.target-row.target-side-left .lineNumButton.left,
-        .diff-row.target-row.target-side-right .lineNumButton.right,
-        .diff-row.target-row.unified .lineNumButton {
-          color: var(--primary-text-color);
-        }
-
-        /**
-          Preparing selected line cells with position relative so it allows a
-          positioned overlay with 'position: absolute'.
-        */
-        .target-row td {
-          position: relative;
-        }
-
-        /**
-          Defines an overlay to the selected line for drawing an outline without
-          blocking user interaction (e.g. text selection).
-        */
-        .target-row td::before {
-          border-width: 0;
-          border-style: solid;
-          border-color: var(--focused-line-outline-color);
-          position: absolute;
-          top: 0;
-          left: 0;
-          width: 100%;
-          height: 100%;
-          pointer-events: none;
-          user-select: none;
-          content: ' ';
-        }
-
-        /**
-          the outline for the selected content cell should be the same in all
-          cases.
-        */
-        .target-row.target-side-left td.left.content::before,
-        .target-row.target-side-right td.right.content::before,
-        .unified.target-row td.content::before {
-          border-width: 1px 1px 1px 0;
-        }
-
-        /**
-          the outline for the sign cell should be always be contiguous
-          top/bottom.
-        */
-        .target-row.target-side-left td.left.sign::before,
-        .target-row.target-side-right td.right.sign::before {
-          border-width: 1px 0;
-        }
-
-        /**
-          For side-by-side we need to select the correct line number to
-          "visually close" the outline.
-        */
-        .side-by-side.target-row.target-side-left td.left.lineNum::before,
-        .side-by-side.target-row.target-side-right td.right.lineNum::before {
-          border-width: 1px 0 1px 1px;
-        }
-
-        /**
-          For unified diff we always start the overlay from the left cell
-        */
-        .unified.target-row td.left:not(.content)::before {
-          border-width: 1px 0 1px 1px;
-        }
-
-        /**
-          For unified diff we should continue the top/bottom border in right
-          line number column.
-        */
-        .unified.target-row td.right:not(.content)::before {
-          border-width: 1px 0;
-        }
-
-        .content {
-          background-color: var(--diff-blank-background-color);
-        }
-
-        /**
-          Describes two states of semantic tokens: whenever a token has a
-          definition that can be navigated to (navigable) and whenever
-          the token is actually clickable to perform this navigation.
-        */
-        .semantic-token.navigable {
-          text-decoration-style: dotted;
-          text-decoration-line: underline;
-        }
-        .semantic-token.navigable.clickable {
-          text-decoration-style: solid;
-          cursor: pointer;
-        }
-
-        /*
-          The file line, which has no contentText, add some margin before the
-          first comment. We cannot add padding the container because we only
-          want it if there is at least one comment thread, and the slotting
-          makes :empty not work as expected.
-        */
-        .content.file slot:first-child::slotted(.comment-thread) {
-          display: block;
-          margin-top: var(--spacing-xs);
-        }
-        .contentText {
-          background-color: var(--view-background-color);
-        }
-        .blank {
-          background-color: var(--diff-blank-background-color);
-        }
-        .image-diff .content {
-          background-color: var(--diff-blank-background-color);
-        }
-        .responsive {
-          width: 100%;
-        }
-        .responsive .contentText {
-          white-space: break-spaces;
-          word-break: break-all;
-        }
-        .lineNumButton,
-        .content {
-          vertical-align: top;
-          white-space: pre;
-        }
-        .contextLineNum,
-        .lineNumButton {
-          -webkit-user-select: none;
-          -moz-user-select: none;
-          -ms-user-select: none;
-          user-select: none;
-
-          color: var(--deemphasized-text-color);
-          padding: 0 var(--spacing-m);
-          text-align: right;
-        }
-        .canComment .lineNumButton {
-          cursor: pointer;
-        }
-        .sign {
-          min-width: 1ch;
-          width: 1ch;
-          background-color: var(--view-background-color);
-        }
-        .sign.blank {
-          background-color: var(--diff-blank-background-color);
-        }
-        .content {
-          /*
-            Set min width since setting width on table cells still allows them
-            to shrink. Do not set max width because CJK
-            (Chinese-Japanese-Korean) glyphs have variable width
-          */
-          min-width: var(--content-width, 80ch);
-          width: var(--content-width, 80ch);
-        }
-        .content.add .contentText .intraline,
-          /* If there are no intraline info, consider everything changed */
-          .content.add.no-intraline-info .contentText,
-          .sign.add.no-intraline-info,
-          .delta.total .content.add .contentText {
-          background-color: var(--dark-add-highlight-color);
-        }
-        .content.add .contentText,
-        .sign.add {
-          background-color: var(--light-add-highlight-color);
-        }
-        .content.remove .contentText .intraline,
-          /* If there are no intraline info, consider everything changed */
-          .content.remove.no-intraline-info .contentText,
-          .delta.total .content.remove .contentText,
-          .sign.remove.no-intraline-info {
-          background-color: var(--dark-remove-highlight-color);
-        }
-        .content.remove .contentText,
-        .sign.remove {
-          background-color: var(--light-remove-highlight-color);
-        }
-
-        .ignoredWhitespaceOnly .sign.no-intraline-info {
-          background-color: var(--view-background-color);
-        }
-
-        /* dueToRebase */
-        .dueToRebase .content.add .contentText .intraline,
-        .delta.total.dueToRebase .content.add .contentText {
-          background-color: var(--dark-rebased-add-highlight-color);
-        }
-        .dueToRebase .content.add .contentText {
-          background-color: var(--light-rebased-add-highlight-color);
-        }
-        .dueToRebase .content.remove .contentText .intraline,
-        .delta.total.dueToRebase .content.remove .contentText {
-          background-color: var(--dark-rebased-remove-highlight-color);
-        }
-        .dueToRebase .content.remove .contentText {
-          background-color: var(--light-rebased-remove-highlight-color);
-        }
-
-        /* dueToMove */
-        .dueToMove .sign.add,
-        .dueToMove .content.add .contentText,
-        .dueToMove .moveControls.movedIn .sign.right,
-        .dueToMove .moveControls.movedIn .moveHeader,
-        .delta.total.dueToMove .content.add .contentText {
-          background-color: var(--diff-moved-in-background);
-        }
-
-        .dueToMove.changed .sign.add,
-        .dueToMove.changed .content.add .contentText,
-        .dueToMove.changed .moveControls.movedIn .sign.right,
-        .dueToMove.changed .moveControls.movedIn .moveHeader,
-        .delta.total.dueToMove.changed .content.add .contentText {
-          background-color: var(--diff-moved-in-changed-background);
-        }
-
-        .dueToMove .sign.remove,
-        .dueToMove .content.remove .contentText,
-        .dueToMove .moveControls.movedOut .moveHeader,
-        .dueToMove .moveControls.movedOut .sign.left,
-        .delta.total.dueToMove .content.remove .contentText {
-          background-color: var(--diff-moved-out-background);
-        }
-
-        .delta.dueToMove .movedIn .moveHeader {
-          --gr-range-header-color: var(--diff-moved-in-label-color);
-        }
-        .delta.dueToMove.changed .movedIn .moveHeader {
-          --gr-range-header-color: var(--diff-moved-in-changed-label-color);
-        }
-        .delta.dueToMove .movedOut .moveHeader {
-          --gr-range-header-color: var(--diff-moved-out-label-color);
-        }
-
-        .moveHeader a {
-          color: inherit;
-        }
-
-        /* ignoredWhitespaceOnly */
-        .ignoredWhitespaceOnly .content.add .contentText .intraline,
-        .delta.total.ignoredWhitespaceOnly .content.add .contentText,
-        .ignoredWhitespaceOnly .content.add .contentText,
-        .ignoredWhitespaceOnly .content.remove .contentText .intraline,
-        .delta.total.ignoredWhitespaceOnly .content.remove .contentText,
-        .ignoredWhitespaceOnly .content.remove .contentText {
-          background-color: var(--view-background-color);
-        }
-
-        .content .contentText gr-diff-text:empty:after,
-        .content .contentText gr-legacy-text:empty:after,
-        .content .contentText:empty:after {
-          /* Newline, to ensure empty lines are one line-height tall. */
-          content: '\\A';
-        }
-
-        /* Context controls */
-        .contextControl {
-          display: var(--context-control-display, table-row-group);
-          background-color: transparent;
-          border: none;
-          --divider-height: var(--spacing-s);
-          --divider-border: 1px;
-        }
-        /* TODO: Is this still used? */
-        .contextControl gr-button gr-icon {
-          /* should match line-height of gr-button */
-          font-size: var(--line-height-mono, 18px);
-        }
-        .contextControl td:not(.lineNumButton) {
-          text-align: center;
-        }
-
-        /**
-          Padding rows behind context controls. Styled as a continuation of the
-          line gutters and code area.
-        */
-        .contextBackground > .contextLineNum {
-          background-color: var(--diff-blank-background-color);
-        }
-        .contextBackground > td:not(.contextLineNum) {
-          background-color: var(--view-background-color);
-        }
-        .contextBackground {
-          /**
-            One line of background behind the context expanders which they can
-            render on top of, plus some padding.
-          */
-          height: calc(var(--line-height-normal) + var(--spacing-s));
-        }
-
-        .dividerCell {
-          vertical-align: top;
-        }
-        .dividerRow.show-both .dividerCell {
-          height: var(--divider-height);
-        }
-        .dividerRow.show-above .dividerCell,
-        .dividerRow.show-above .dividerCell {
-          height: 0;
-        }
-
-        .br:after {
-          /* Line feed */
-          content: '\\A';
-        }
-        .tab {
-          display: inline-block;
-        }
-        .tab-indicator:before {
-          color: var(--diff-tab-indicator-color);
-          /* >> character */
-          content: '\\00BB';
-          position: absolute;
-        }
-        .special-char-indicator {
-          /* spacing so elements don't collide */
-          padding-right: var(--spacing-m);
-        }
-        .special-char-indicator:before {
-          color: var(--diff-tab-indicator-color);
-          content: '•';
-          position: absolute;
-        }
-        .special-char-warning {
-          /* spacing so elements don't collide */
-          padding-right: var(--spacing-m);
-        }
-        .special-char-warning:before {
-          color: var(--warning-foreground);
-          content: '!';
-          position: absolute;
-        }
-        /**
-          Is defined after other background-colors, such that this
-          rule wins in case of same specificity.
-        */
-        .trailing-whitespace,
-        .content .contentText .trailing-whitespace,
-        .trailing-whitespace .intraline,
-        .content .contentText .trailing-whitespace .intraline {
-          border-radius: var(--border-radius, 4px);
-          background-color: var(--diff-trailing-whitespace-indicator);
-        }
-        #diffHeader {
-          background-color: var(--table-header-background-color);
-          border-bottom: 1px solid var(--border-color);
-          color: var(--link-color);
-          padding: var(--spacing-m) 0 var(--spacing-m) 48px;
-        }
-        #diffTable {
-          /* for gr-selection-action-box positioning */
-          position: relative;
-        }
-        #diffTable:focus {
-          outline: none;
-        }
-        #loadingError,
-        #sizeWarning {
-          display: block;
-          margin: var(--spacing-l) auto;
-          max-width: 60em;
-          text-align: center;
-        }
-        #loadingError {
-          color: var(--error-text-color);
-        }
-        #sizeWarning gr-button {
-          margin: var(--spacing-l);
-        }
-        .target-row td.blame {
-          background: var(--diff-selection-background-color);
-        }
-        td.lost div {
-          background-color: var(--info-background);
-        }
-        td.lost div.lost-message {
-          font-family: var(--font-family, 'Roboto');
-          font-size: var(--font-size-normal, 14px);
-          line-height: var(--line-height-normal);
-          padding: var(--spacing-s) 0;
-        }
-        td.lost div.lost-message gr-icon {
-          padding: 0 var(--spacing-s) 0 var(--spacing-m);
-          color: var(--blue-700);
-        }
-
-        col.sign,
-        td.sign {
-          display: none;
-        }
-
-        /* Sign column should only be shown in high-contrast mode. */
-        :host(.with-sign-col) col.sign {
-          display: table-column;
-        }
-        :host(.with-sign-col) td.sign {
-          display: table-cell;
-        }
-        col.blame {
-          display: none;
-        }
-        td.blame {
-          display: none;
-          padding: 0 var(--spacing-m);
-          white-space: pre;
-        }
-        :host(.showBlame) col.blame {
-          display: table-column;
-        }
-        :host(.showBlame) td.blame {
-          display: table-cell;
-        }
-        td.blame > span {
-          opacity: 0.6;
-        }
-        td.blame > span.startOfRange {
-          opacity: 1;
-        }
-        td.blame .blameDate {
-          font-family: var(--monospace-font-family);
-          color: var(--link-color);
-          text-decoration: none;
-        }
-        .responsive td.blame {
-          overflow: hidden;
-          width: 200px;
-        }
-        /** Support the line length indicator **/
-        .responsive td.content .contentText {
-          /**
-            Same strategy as in
-            https://stackoverflow.com/questions/1179928/how-can-i-put-a-vertical-line-down-the-center-of-a-div
-          */
-          background-image: linear-gradient(
-            var(--line-length-indicator-color),
-            var(--line-length-indicator-color)
-          );
-          background-size: 1px 100%;
-          background-position: var(--line-limit-marker) 0;
-          background-repeat: no-repeat;
-        }
-        .newlineWarning {
-          color: var(--deemphasized-text-color);
-          text-align: center;
-        }
-        .newlineWarning.hidden {
-          display: none;
-        }
-        .lineNum.COVERED .lineNumButton {
-          color: var(
-            --coverage-covered-line-num-color,
-            var(--deemphasized-text-color)
-          );
-          background-color: var(--coverage-covered, #e0f2f1);
-        }
-        .lineNum.NOT_COVERED .lineNumButton {
-          color: var(
-            --coverage-covered-line-num-color,
-            var(--deemphasized-text-color)
-          );
-          background-color: var(--coverage-not-covered, #ffd1a4);
-        }
-        .lineNum.PARTIALLY_COVERED .lineNumButton {
-          color: var(
-            --coverage-covered-line-num-color,
-            var(--deemphasized-text-color)
-          );
-          background: linear-gradient(
-            to right bottom,
-            var(--coverage-not-covered, #ffd1a4) 0%,
-            var(--coverage-not-covered, #ffd1a4) 50%,
-            var(--coverage-covered, #e0f2f1) 50%,
-            var(--coverage-covered, #e0f2f1) 100%
-          );
-        }
-
-        // TODO: Investigate whether this CSS is still necessary.
-        /** BEGIN: Select and copy for Polymer 2 */
-        /**
-          Below was copied and modified from the original css in
-          gr-diff-selection.html
-        */
-        .content,
-        .contextControl,
-        .blame {
-          -webkit-user-select: none;
-          -moz-user-select: none;
-          -ms-user-select: none;
-          user-select: none;
-        }
-
-        .selected-left:not(.selected-comment)
-          .side-by-side
-          .left
-          + .content
-          .contentText,
-        .selected-right:not(.selected-comment)
-          .side-by-side
-          .right
-          + .content
-          .contentText,
-        .selected-left:not(.selected-comment)
-          .unified
-          .left.lineNum
-          ~ .content:not(.both)
-          .contentText,
-        .selected-right:not(.selected-comment)
-          .unified
-          .right.lineNum
-          ~ .content
-          .contentText,
-        .selected-left.selected-comment .side-by-side .left + .content .message,
-        .selected-right.selected-comment
-          .side-by-side
-          .right
-          + .content
-          .message
-          :not(.collapsedContent),
-        .selected-comment .unified .message :not(.collapsedContent),
-        .selected-blame .blame {
-          -webkit-user-select: text;
-          -moz-user-select: text;
-          -ms-user-select: text;
-          user-select: text;
-        }
-
-        /** Make comments and check results selectable when selected */
-        .selected-left.selected-comment
-          ::slotted(.comment-thread[diff-side='left']),
-        .selected-right.selected-comment
-          ::slotted(.comment-thread[diff-side='right']) {
-          -webkit-user-select: text;
-          -moz-user-select: text;
-          -ms-user-select: text;
-          user-select: text;
-        }
-        /** END: Select and copy for Polymer 2 */
-
-        .whitespace-change-only-message {
-          background-color: var(--diff-context-control-background-color);
-          border: 1px solid var(--diff-context-control-border-color);
-          text-align: center;
-        }
-
-        .token-highlight {
-          background-color: var(--token-highlighting-color, #fffd54);
-        }
-
-        gr-selection-action-box {
-          /**
-          * Needs z-index to appear above wrapped content, since it's inserted
-          * into DOM before it.
-          */
-          z-index: 10;
-        }
-
-        gr-diff-image-new,
-        gr-diff-image-old,
-        gr-diff-section,
-        gr-context-controls-section,
-        gr-diff-row {
-          display: contents;
-        }
-      `,
+      grDiffStyles,
     ];
   }