[QuickView] Add tab-index focus test for text 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
text file in its content area.

Tab past the content panel to skip over checking the focus on the content
webview.

Bug: 907380
Change-Id: Ia800bf7a04633376d7c355e0947d2fcaa9bf72f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2000281
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731868}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -465,6 +465,7 @@ WRAPPED_INSTANTIATE_TEST_SUITE_P(
         TestCase("openQuickViewRemovablePartitions"),
         TestCase("openQuickViewMtp"),
         TestCase("openQuickViewTabIndexImage"),
+        TestCase("openQuickViewTabIndexText"),
         TestCase("pressEnterOnInfoBoxToOpenClose"),
         TestCase("closeQuickView"),
         TestCase("cantOpenQuickViewWithMultipleFiles"),

ui/file_manager/integration_tests/file_manager/quick_view.js

@@ -1338,4 +1338,41 @@
       await remoteCall.waitForElement(appId, query.query);
     }
   };
+
+  /**
+   * Tests the tab-index focus order when sending tab keys when a text file is
+   * shown in Quick View.
+   */
+  testcase.openQuickViewTabIndexText = async () => {
+    // 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']},
+      {'query': ['#quick-view']},  // Tab past the content panel.
+      {'query': ['#quick-view', '[aria-label="Back"]:focus']},
+    ];
+
+    // Open Files app on Downloads containing ENTRIES.tallText.
+    const appId = await setupAndWaitUntilReady(
+        RootPath.DOWNLOADS, [ENTRIES.tallText], []);
+
+    // Open the file in Quick View.
+    await openQuickView(appId, ENTRIES.tallText.nameText);
+
+    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);
+    }
+  };
 })();