Update kAccessibilityFocusFallsbackToWidgetKey

- Update kAccessibilityFocusFallsbackToWidgetKey depending on whether
  ChromeVox or TalkBack is used for the window.
- This CL fixes the logic to update window properties. AxTree can arrive
  to the helper bridge after a window is activated. This CL adds a logic
  to fix it.

      confirm that it works.

Bug: 866793
Test: Navigate Android window with TalkBack by using keyboard and
Change-Id: I911c77229c9a6f338fcdadd81ea5642aaefae084
Reviewed-on: https://chromium-review.googlesource.com/1148099Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Yuki Awano <yawano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578521}

chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge.cc

@@ -278,6 +278,10 @@ void ArcAccessibilityHelperBridge::OnAccessibilityEvent(
               ax::mojom::Event::kTextSelectionChanged, true);
         }
       }
+    } else if (!is_notification_event &&
+               event_data->event_type ==
+                   arc::mojom::AccessibilityEventType::WINDOW_STATE_CHANGED) {
+      UpdateWindowProperties(GetActiveWindow());
     }
 
     return;
@@ -560,6 +564,8 @@ void ArcAccessibilityHelperBridge::UpdateWindowProperties(
   window->SetProperty(aura::client::kAccessibilityTouchExplorationPassThrough,
                       use_talkback);
   window->SetProperty(ash::kSearchKeyAcceleratorReservedKey, use_talkback);
+  window->SetProperty(aura::client::kAccessibilityFocusFallsbackToWidgetKey,
+                      !use_talkback);
 }
 
 aura::Window* ArcAccessibilityHelperBridge::GetActiveWindow() {

components/exo/shell_surface_base.cc

@@ -1199,10 +1199,6 @@ void ShellSurfaceBase::CreateShellSurfaceWidget(
 
   aura::Window* window = widget_->GetNativeWindow();
   window->SetName("ExoShellSurface");
-  // TODO(yawano): This needs to be set to false if TalkBack is handling this
-  //               window.
-  window->SetProperty(aura::client::kAccessibilityFocusFallsbackToWidgetKey,
-                      true);
   window->AddChild(host_window());
   // Use DESCENDANTS_ONLY event targeting policy for mus/mash.
   // TODO(https://crbug.com/839521): Revisit after event dispatching code is