Ash Tray: Fix ChromeVox crash in when opening message center in tablet mode.

The current TrayBubbleView::Delegate implementation is causing the message
center to be activated before it is ready, so we will just use the default stub
implementation.

Change-Id: Ibc73de7d1516d2ebd72e870ab5d3db3963887845
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1938253Reviewed-by: Ahmed Mehfooz <amehfooz@chromium.org>
Commit-Queue: Ahmed Mehfooz <amehfooz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719460}

ash/system/message_center/unified_message_center_bubble.cc

@@ -10,7 +10,6 @@
 #include "ash/style/ash_color_provider.h"
 #include "ash/style/default_color_constants.h"
 #include "ash/system/message_center/unified_message_center_view.h"
-#include "ash/system/tray/tray_bubble_view.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_event_filter.h"
 #include "ash/system/unified/unified_system_tray.h"
@@ -66,7 +65,7 @@ class UnifiedMessageCenterBubble::Border : public ui::LayerDelegate {
 UnifiedMessageCenterBubble::UnifiedMessageCenterBubble(UnifiedSystemTray* tray)
     : tray_(tray), border_(std::make_unique<Border>()) {
   TrayBubbleView::InitParams init_params;
-  init_params.delegate = tray;
+  init_params.delegate = this;
   // Anchor within the overlay container.
   init_params.parent_window = tray->GetBubbleWindowContainer();
   init_params.anchor_mode = TrayBubbleView::AnchorMode::kRect;

ash/system/message_center/unified_message_center_bubble.h

@@ -6,6 +6,7 @@
 #define ASH_SYSTEM_MESSAGE_CENTER_UNIFIED_MESSAGE_CENTER_BUBBLE_H_
 
 #include "ash/system/tray/tray_bubble_base.h"
+#include "ash/system/tray/tray_bubble_view.h"
 #include "ui/views/view_observer.h"
 #include "ui/views/widget/widget_observer.h"
 
@@ -15,13 +16,13 @@ class Widget;
 
 namespace ash {
 
-class TrayBubbleView;
 class UnifiedSystemTray;
 class UnifiedMessageCenterView;
 
 // Manages the bubble that contains UnifiedMessageCenterView.
 // Shows the bubble on the constructor, and closes the bubble on the destructor.
 class ASH_EXPORT UnifiedMessageCenterBubble : public TrayBubbleBase,
+                                              public TrayBubbleView::Delegate,
                                               public views::ViewObserver,
                                               public views::WidgetObserver {
  public: