Ensure that mask layer is of the same size as the owning layer.

ui/views/bubble/tray_bubble_view.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_
 #define UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 133 matching lines @@
 
  protected:
   // Overridden from views::BubbleDialogDelegateView.
   int GetDialogButtons() const override;
 
   // Overridden from views::View.
   void ChildPreferredSizeChanged(View* child) override;
   void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) override;
 
+  void SizeToContents() override;

[James Cook, 2017/06/13 20:43:46]

nit: move this up to line 148 to put it with the other BubbleDialogDelegateView
method

[sunxd, 2017/06/13 22:13:47]

Done.

+
  private:
   InitParams params_;
   BoxLayout* layout_;
   Delegate* delegate_;
   int preferred_width_;
   // |bubble_border_| and |owned_bubble_border_| point to the same thing, but
   // the latter ensures we don't leak it before passing off ownership.
   BubbleBorder* bubble_border_;
   std::unique_ptr<views::BubbleBorder> owned_bubble_border_;
   std::unique_ptr<internal::TrayBubbleContentMask> bubble_content_mask_;
   bool is_gesture_dragging_;
 
   // True once the mouse cursor was actively moved by the user over the bubble.
   // Only then the OnMouseExitedView() event will get passed on to listeners.
   bool mouse_actively_entered_;
 
   // Used to find any mouse movements.
   std::unique_ptr<MouseWatcher> mouse_watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBubbleView);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_