Remove lit diff `isVisible` optimization temporarily

The optimization is still causing some problems, and thus it gets in the
way of the migration from legacy diff to lit diff. Let's first make a
smooth transition, and then come back later to the separate concern of
improving the diff performance.

Release-Notes: skip
Google-Bug-Id: b/237393560
Change-Id: If428ab744e3729dae30c4f9ce3d669ae3d544263

polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row.ts

diff --git a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row.ts b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row.ts
index 4783042..f1ce0e3 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row.ts
@@ -60,14 +60,6 @@
   layers: DiffLayer[] = [];
 
   /**
-   * While not visible we are trying to optimize rendering performance by
-   * rendering a simpler version of the diff. Once this has become true it
-   * cannot be set back to false.
-   */
-  @state()
-  isVisible = false;
-
-  /**
    * Semantic DOM diff testing does not work with just table fragments, so when
    * running such tests the render() method has to wrap the DOM in a proper
    * <table> element.
@@ -120,7 +112,6 @@
    * `this.layersApplied = true`.
    */
   private async updateLayers(side: Side) {
-    if (!this.isVisible) return;
     const line = this.line(side);
     const contentEl = this.contentRef(side).value;
     const lineNumberEl = this.lineNumberRef(side).value;
@@ -139,25 +130,8 @@
     this.layersApplied = true;
   }
 
-  private renderInvisible() {
-    return html`
-      <tr>
-        <td class="gr-diff blame"></td>
-        <td class="gr-diff left"></td>
-        <td class="gr-diff left content">
-          <div>${this.left?.text ?? ''}</div>
-        </td>
-        <td class="gr-diff right"></td>
-        <td class="gr-diff right content">
-          <div>${this.right?.text ?? ''}</div>
-        </td>
-      </tr>
-    `;
-  }
-
   override render() {
     if (!this.left || !this.right) return;
-    if (!this.isVisible) return this.renderInvisible();
     const row = html`
       <tr
         ${ref(this.tableRowRef)}

polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row_test.ts

diff --git a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row_test.ts b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row_test.ts
index 4e8bb62..da3230f 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row_test.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-row_test.ts
@@ -15,7 +15,6 @@
 
   setup(async () => {
     element = await fixture<GrDiffRow>(html`<gr-diff-row></gr-diff-row>`);
-    element.isVisible = true;
     element.addTableWrapperForTesting = true;
     await element.updateComplete;
   });

polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section.ts

diff --git a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section.ts b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section.ts
index 16c7cb3..e0dd6bc 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section.ts
@@ -22,7 +22,6 @@
 import '../gr-context-controls/gr-context-controls';
 import '../gr-range-header/gr-range-header';
 import './gr-diff-row';
-import {whenVisible} from '../../../utils/dom-util';
 
 @customElement('gr-diff-section')
 export class GrDiffSection extends LitElement {
@@ -42,13 +41,6 @@
   layers: DiffLayer[] = [];
 
   /**
-   * While not visible we are trying to optimize rendering performance by
-   * rendering a simpler version of the diff.
-   */
-  @state()
-  isVisible = false;
-
-  /**
    * Semantic DOM diff testing does not work with just table fragments, so when
    * running such tests the render() method has to wrap the DOM in a proper
    * <table> element.
@@ -67,12 +59,6 @@
     return this;
   }
 
-  override connectedCallback() {
-    super.connectedCallback();
-    // TODO: Refine this obviously simplistic approach to optimized rendering.
-    whenVisible(this.parentElement!, () => (this.isVisible = true), 1000);
-  }
-
   override render() {
     if (!this.group) return;
     const extras: string[] = [];
@@ -100,7 +86,6 @@
               .layers=${this.layers}
               .lineLength=${this.diffPrefs?.line_length ?? 80}
               .tabSize=${this.diffPrefs?.tab_size ?? 2}
-              .isVisible=${this.isVisible}
             >
             </gr-diff-row>
           `;

polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section_test.ts

diff --git a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section_test.ts b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section_test.ts
index 363b001..14efa22 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section_test.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-section_test.ts
@@ -19,7 +19,6 @@
       html`<gr-diff-section></gr-diff-section>`
     );
     element.addTableWrapperForTesting = true;
-    element.isVisible = true;
     await element.updateComplete;
   });