Remove the `loading` feature from the file-list

It hinders the migration of the file-list to using the files model.
Well, it makes it more complicated.

The benefit of the `loading` feature is to just overlay the file list
with opacity:0.5.

Loading files is extremely fast, so it is actually hard to see any
instances of this overlay apart from a quick flash.

I think we could also just wipe the list of files while loading.

Or if we feel there was a benefit after all, then we can bring back
the feature after the migration to files model.

Release-Notes: skip
Change-Id: I227c72560731f922005b57d58faffe478ffbaccd

polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts

diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
index 8f5d4f9..3b3f1c5 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
@@ -17,7 +17,7 @@
 import '../../shared/gr-tooltip-content/gr-tooltip-content';
 import '../../shared/gr-copy-clipboard/gr-copy-clipboard';
 import '../../shared/gr-file-status-chip/gr-file-status-chip';
-import {asyncForeach, debounce, DelayedTask} from '../../../utils/async-util';
+import {asyncForeach} from '../../../utils/async-util';
 import {FilesExpandedState} from '../gr-file-list-constants';
 import {pluralize} from '../../../utils/string-util';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation';
@@ -82,7 +82,6 @@
 export const DEFAULT_NUM_FILES_SHOWN = 200;
 
 const WARN_SHOW_ALL_THRESHOLD = 1000;
-const LOADING_DEBOUNCE_INTERVAL = 100;
 
 const SIZE_BAR_MAX_WIDTH = 61;
 const SIZE_BAR_GAP_WIDTH = 1;
@@ -244,9 +243,6 @@
   @state()
   displayLine?: boolean;
 
-  @state()
-  loading?: boolean;
-
   // Private but used in tests.
   @state()
   showSizeBars = true;
@@ -263,8 +259,6 @@
 
   private cancelForEachDiff?: () => void;
 
-  loadingTask?: DelayedTask;
-
   @state()
   private dynamicHeaderEndpoints?: string[];
 
@@ -334,9 +328,6 @@
           /* inline-block instead of block, such that it can control width */
           display: inline-block;
         }
-        :host(.loading) .row {
-          opacity: 0.5;
-        }
         :host(.editMode) .hideOnEdit {
           display: none;
         }
@@ -737,16 +728,11 @@
       changedProperties.has('filesByPath') ||
       changedProperties.has('changeComments') ||
       changedProperties.has('patchRange') ||
-      changedProperties.has('reviewed') ||
-      changedProperties.has('loading')
+      changedProperties.has('reviewed')
     ) {
       changedProperties.set('files', this.files);
       this.computeFiles();
     }
-    if (changedProperties.has('loading')) {
-      // Should run after files has been updated.
-      this.loadingChanged();
-    }
     if (changedProperties.has('files')) {
       this.filesChanged();
     }
@@ -822,7 +808,6 @@
     this.diffCursor?.dispose();
     this.fileCursor.unsetCursor();
     this.cancelDiffs();
-    this.loadingTask?.cancel();
     for (const cleanup of this.cleanups) cleanup();
     this.cleanups = [];
     super.disconnectedCallback();
@@ -1404,7 +1389,6 @@
 
   async reload() {
     if (!this.changeNum || !this.patchRange?.patchNum) return;
-    this.loading = true;
     this.collapseAllDiffs();
 
     this.filesByPath = await this.restApiService.getChangeOrEditFiles(
@@ -1412,7 +1396,6 @@
       this.patchRange
     );
 
-    this.loading = false;
     this.detectChromiteButler();
     this.reporting.fileListDisplayed();
   }
@@ -2024,15 +2007,12 @@
       this.filesByPath === undefined ||
       this.changeComments === undefined ||
       this.patchRange === undefined ||
-      this.reviewed === undefined ||
-      this.loading === undefined
+      this.reviewed === undefined
     ) {
       return;
     }
     // Await all promises resolving from reload. @See Issue 9057
-    if (this.loading || !this.changeComments) {
-      return;
-    }
+    if (!this.changeComments) return;
     const commentedPaths = this.changeComments.getPaths(this.patchRange);
     const files: FileNameToReviewedFileInfoMap = {...this.filesByPath};
     addUnmodifiedFiles(files, commentedPaths);
@@ -2292,24 +2272,6 @@
     this.displayLine = false;
   }
 
-  /**
-   * Update the loading class for the file list rows. The update is inside a
-   * debouncer so that the file list doesn't flash gray when the API requests
-   * are reasonably fast.
-   */
-  private loadingChanged() {
-    const loading = this.loading;
-    this.loadingTask = debounce(
-      this.loadingTask,
-      () => {
-        // Only show set the loading if there have been files loaded to show. In
-        // this way, the gray loading style is not shown on initial loads.
-        this.classList.toggle('loading', loading && !!this.files.length);
-      },
-      LOADING_DEBOUNCE_INTERVAL
-    );
-  }
-
   private computeReviewedClass(isReviewed?: boolean) {
     return isReviewed ? 'isReviewed' : '';
   }

polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.ts

diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.ts b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.ts
index ab7089a..83033bf 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.ts
@@ -22,12 +22,10 @@
   EDIT,
   NumericChangeId,
   PARENT,
-  PatchRange,
   RepoName,
   RevisionPatchSetNum,
   Timestamp,
   UrlEncodedCommentId,
-  FileNameToFileInfoMap,
 } from '../../../types/common';
 import {createCommentThreads} from '../../../utils/comment-util';
 import {
@@ -90,7 +88,6 @@
 
       element = basicFixture.instantiate();
 
-      element.loading = false;
       element.diffPrefs = {
         context: 10,
         tab_size: 8,
@@ -1504,57 +1501,6 @@
       assert.isTrue(reviewStub.calledWithExactly('p', true));
     });
 
-    test('loadingChanged fired from reload in debouncer', async () => {
-      const reloadBlocker = mockPromise<FileNameToFileInfoMap | undefined>();
-      stubRestApi('getChangeOrEditFiles').returns(
-        reloadBlocker.then(() => {
-          return {'foo.bar': {size: 0, size_delta: 0}};
-        })
-      );
-      stubRestApi('getReviewedFiles').resolves(undefined);
-      stubRestApi('getDiffPreferences').resolves(createDefaultDiffPrefs());
-
-      element.changeNum = 123 as NumericChangeId;
-      element.patchRange = {patchNum: 12 as RevisionPatchSetNum} as PatchRange;
-      element.filesByPath = {'foo.bar': {size: 0, size_delta: 0}};
-      element.change = {
-        ...createParsedChange(),
-        _number: 123 as NumericChangeId,
-      };
-      await element.updateComplete;
-      await flush();
-
-      const reloaded = element.reload();
-      await element.updateComplete;
-      assert.isTrue(element.loading);
-      assert.isFalse(element.classList.contains('loading'));
-      element.loadingTask!.flush();
-      assert.isTrue(element.classList.contains('loading'));
-
-      reloadBlocker.resolve();
-      await reloaded;
-
-      assert.isFalse(element.loading);
-      element.loadingTask!.flush();
-      assert.isFalse(element.classList.contains('loading'));
-    });
-
-    test('loadingChanged does not set class when there are no files', () => {
-      element.changeNum = 123 as NumericChangeId;
-      element.patchRange = {patchNum: 12 as RevisionPatchSetNum} as PatchRange;
-      element.change = {
-        ...createParsedChange(),
-        _number: 123 as NumericChangeId,
-      };
-      element.reload();
-
-      assert.isTrue(element.loading);
-
-      element.loadingTask!.flush();
-
-      assert.isFalse(element.classList.contains('loading'));
-    });
-
     suite('for merge commits', () => {
       let filesStub: sinon.SinonStub;
 
@@ -2024,7 +1970,6 @@
       };
       reviewFileStub = sinon.stub(element, 'reviewFile');
 
-      element.loading = false;
       element.numFilesShown = 75;
       element.selectedIndex = 0;
       element.filesByPath = {