Keeps auto-hide shelf showing after opening the system tray

Due to the side effect from https://crrev.com/c/1988855, auto-hide shelf
is hidden after opening the system tray. Update on the shelf's
visibility state is triggered by the visibility change of system tray.
However, calculation on the auto-hide state depends on the state of
tray bubbles which are created/destructed after the visibility change.
This CL delays the update on the shelf's state when the visibility of
system tray changes. In addition, a test case is added for this
scenario.

Bug: 1046464
Change-Id: I72d48b5872ca9efc8160c9fd6bba6bd55addfa43
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2028766Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737437}

ash/shelf/hotseat_widget_unittest.cc

@@ -1268,6 +1268,8 @@ TEST_P(HotseatWidgetTest, ExitOverviewWithClickOnHotseat) {
 // Hides the hotseat if the hotseat is in kExtendedMode and the system tray
 // is about to show (see https://crbug.com/1028321).
 TEST_P(HotseatWidgetTest, DismissHotseatWhenSystemTrayShows) {
+  GetPrimaryShelf()->SetAutoHideBehavior(shelf_auto_hide_behavior());
+
   TabletModeControllerTestApi().EnterTabletMode();
   std::unique_ptr<aura::Window> window =
       AshTestBase::CreateTestWindow(gfx::Rect(0, 0, 400, 400));
@@ -1276,15 +1278,36 @@ TEST_P(HotseatWidgetTest, DismissHotseatWhenSystemTrayShows) {
   SwipeUpOnShelf();
   ASSERT_EQ(HotseatState::kExtended, GetShelfLayoutManager()->hotseat_state());
 
-  // Activates the system tray when hotseat is in kExtended mode.
+  // Activates the system tray when hotseat is in kExtended mode and waits for
+  // the update in system tray to finish.
   StatusAreaWidget* status_area_widget = GetShelfWidget()->status_area_widget();
   const gfx::Point status_area_widget_center =
       status_area_widget->GetNativeView()->GetBoundsInScreen().CenterPoint();
   GetEventGenerator()->GestureTapAt(status_area_widget_center);
+  base::RunLoop().RunUntilIdle();
 
   // Expects that the system tray shows and the hotseat is hidden.
   EXPECT_EQ(HotseatState::kHidden, GetShelfLayoutManager()->hotseat_state());
   EXPECT_TRUE(status_area_widget->unified_system_tray()->IsBubbleShown());
+
+  // Early out since the remaining code is only meaningful for auto-hide shelf.
+  if (GetPrimaryShelf()->auto_hide_behavior() !=
+      ShelfAutoHideBehavior::kAlways) {
+    return;
+  }
+
+  // Auto-hide shelf should show when opening the system tray.
+  EXPECT_EQ(ShelfAutoHideState::SHELF_AUTO_HIDE_SHOWN,
+            GetShelfLayoutManager()->auto_hide_state());
+
+  // Auto-hide shelf should hide when closing the system tray.
+  GetEventGenerator()->GestureTapAt(status_area_widget_center);
+
+  // Waits for the system tray to be closed.
+  base::RunLoop().RunUntilIdle();
+
+  EXPECT_EQ(ShelfAutoHideState::SHELF_AUTO_HIDE_HIDDEN,
+            GetShelfLayoutManager()->auto_hide_state());
 }
 
 // Tests that the work area updates once each when going to/from tablet mode

ash/shelf/scrollable_shelf_view.h

@@ -17,6 +17,7 @@
 #include "ash/shelf/shelf_container_view.h"
 #include "ash/shelf/shelf_tooltip_delegate.h"
 #include "ash/shelf/shelf_view.h"
+#include "base/cancelable_callback.h"
 #include "ui/compositor/layer_animation_observer.h"
 #include "ui/views/animation/ink_drop_host_view.h"
 #include "ui/views/context_menu_controller.h"

ash/shelf/shelf_layout_manager.cc

@@ -1134,15 +1134,19 @@ void ShelfLayoutManager::OnCenterVisibilityChanged(
   if (!chromeos::switches::ShouldShowShelfHotseat())
     return;
 
-  if (visibility != message_center::VISIBILITY_MESSAGE_CENTER ||
-      hotseat_state() != HotseatState::kExtended) {
-    return;
-  }
+  // Uses base::CancelableClosure to handle two edge cases: (1)
+  // ShelfLayoutManager is destructed before the callback runs. (2) The previous
+  // callback is still pending.
+  visibility_update_for_tray_callback_.Reset(base::BindOnce(
+      &ShelfLayoutManager::UpdateVisibilityStateForSystemTrayChange,
+      base::Unretained(this), visibility));
 
-  // Hides the hotseat when the hotseat is in kExtended mode and the system
-  // tray shows.
-  base::AutoReset<bool> reset(&should_hide_hotseat_, true);
-  UpdateVisibilityState();
+  // OnCenterVisibilityChanged is called when the visibility of system tray
+  // is set, which is before the tray bubble is created/destructed. Meanwhile,
+  // we rely on the state of tray bubble to calculate the auto-hide state.
+  // Use ThreadTaskRunnerHandle to specify that the task runs on the UI thread.
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, visibility_update_for_tray_callback_.callback());
 }
 
 void ShelfLayoutManager::SuspendWorkAreaUpdate() {
@@ -2825,4 +2829,18 @@ bool ShelfLayoutManager::IsWindowDragInProgress() const {
   return window_drag_controller_ && window_drag_controller_->drag_started();
 }
 
+void ShelfLayoutManager::UpdateVisibilityStateForSystemTrayChange(
+    message_center::Visibility visibility) {
+  base::Optional<base::AutoReset<bool>> reset;
+
+  // Hides the hotseat when the hotseat is in kExtended mode and the system tray
+  // shows.
+  if (visibility == message_center::Visibility::VISIBILITY_MESSAGE_CENTER &&
+      hotseat_state() == HotseatState::kExtended) {
+    reset.emplace(&should_hide_hotseat_, true);
+  }
+
+  UpdateVisibilityState();
+}
+
 }  // namespace ash

ash/shelf/shelf_layout_manager.h

@@ -485,6 +485,10 @@ class ASH_EXPORT ShelfLayoutManager
   void MaybeCancelWindowDrag();
   bool IsWindowDragInProgress() const;
 
+  // Updates the visibility state because of the change on the system tray.
+  void UpdateVisibilityStateForSystemTrayChange(
+      message_center::Visibility visibility);
+
   // True when inside UpdateBoundsAndOpacity() method. Used to prevent calling
   // UpdateBoundsAndOpacity() again from SetChildBounds().
   bool updating_bounds_ = false;
@@ -635,6 +639,10 @@ class ASH_EXPORT ShelfLayoutManager
   // Tracks whether the shelf is currently dimmed for inactivity.
   bool dimmed_for_inactivity_ = false;
 
+  // Callback to update the shelf's state when the visibility of system tray
+  // changes.
+  base::CancelableOnceClosure visibility_update_for_tray_callback_;
+
   // Records the presentation time for hotseat dragging.
   std::unique_ptr<PresentationTimeRecorder> hotseat_presentation_time_recorder_;