[QuickView] Add tab-index focus test for video files

Add a test that tab-index key focus works correctly (the tab-indexable
elements are cycled through in order) when Quick View is displaying a
video file in its content panel.

Tab past the content panel to skip over checking the focus on the content
webview/video: these can have multiple internal elements that can
take the focus and our test should be independent of that.

Bug: 907380
Change-Id: Ie7f6de4a4ab5487ed62fc30361674ac1d55de057
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2004172
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732263}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -467,6 +467,7 @@ WRAPPED_INSTANTIATE_TEST_SUITE_P(
         TestCase("openQuickViewTabIndexImage"),
         TestCase("openQuickViewTabIndexText"),
         TestCase("openQuickViewTabIndexAudio"),
+        TestCase("openQuickViewTabIndexVideo"),
         TestCase("pressEnterOnInfoBoxToOpenClose"),
         TestCase("closeQuickView"),
         TestCase("openQuickViewFromDirectoryTree")));

ui/file_manager/integration_tests/file_manager/quick_view.js

@@ -1397,4 +1397,59 @@
       }
     }
   };
+
+  /**
+   * Tests the tab-index focus order when sending tab keys when a video file is
+   * shown in Quick View.
+   */
+  testcase.openQuickViewTabIndexVideo = async () => {
+    // Open Files app on Downloads containing ENTRIES.webm video.
+    const appId =
+        await setupAndWaitUntilReady(RootPath.DOWNLOADS, [ENTRIES.webm], []);
+
+    // Open the file in Quick View.
+    await openQuickView(appId, ENTRIES.webm.nameText);
+
+    // Prepare a list of tab-index focus queries.
+    const tabQueries = [
+      {'query': ['#quick-view', '[aria-label="Back"]:focus']},
+      {'query': ['#quick-view', '[aria-label="Open"]:focus']},
+      {'query': ['#quick-view', '[aria-label="File info"]:focus']},
+    ];
+
+    for (const query of tabQueries) {
+      // Make the browser dispatch a tab key event to FilesApp.
+      const result = await sendTestMessage(
+          {name: 'dispatchTabKey', shift: query.shift || false});
+      chrome.test.assertEq(
+          result, 'tabKeyDispatched', 'Tab key dispatch failure');
+
+      // Note: Allow 500ms between key events to filter out the focus
+      // traversal problems noted in crbug.com/907380#c10.
+      await wait(500);
+
+      // Check: the queried element should gain the focus.
+      await remoteCall.waitForElement(appId, query.query);
+    }
+
+    // Send tab keys until Back gains the focus again.
+    while (true) {
+      // Make the browser dispatch a tab key event to FilesApp.
+      const result =
+          await sendTestMessage({name: 'dispatchTabKey', shift: false});
+      chrome.test.assertEq(
+          result, 'tabKeyDispatched', 'Tab key dispatch failure');
+
+      // Note: Allow 500ms between key events to filter out the focus
+      // traversal problems noted in crbug.com/907380#c10.
+      await wait(500);
+
+      // Check: back should eventually get the focus again.
+      const activeElement = await remoteCall.callRemoteTestUtil(
+          'deepGetActiveElement', appId, []);
+      if (activeElement.attributes['aria-label'] === 'Back') {
+        break;
+      }
+    }
+  };
 })();