Apply new MD shadows to CrOS tray bubbles.

ui/views/bubble/bubble_border.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_BUBBLE_BORDER_H_
 #define UI_VIEWS_BUBBLE_BUBBLE_BORDER_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
@@ skipping 82 matching lines @@
     RIGHT_CENTER  = CENTER | VERTICAL | RIGHT,
     NONE  = 16,  // No arrow. Positioned under the supplied rect.
     FLOAT = 17,  // No arrow. Centered over the supplied rect.
   };
 
   enum Shadow {
     NO_SHADOW = 0,
     NO_SHADOW_OPAQUE_BORDER,
     BIG_SHADOW,
     SMALL_SHADOW,
+    // NO_ASSETS borders don't draw a stroke or a shadow. This is used for
+    // platforms that provide their own shadows.
     NO_ASSETS,
     SHADOW_COUNT,
   };
 
   // The position of the bubble in relation to the anchor.
   enum BubbleAlignment {
     // The tip of the arrow points to the middle of the anchor.
     ALIGN_ARROW_TO_MID_ANCHOR,
     // The edge nearest to the arrow is lined up with the edge of the anchor.
     ALIGN_EDGE_TO_ANCHOR_EDGE,
@@ skipping 155 matching lines @@
 
  private:
   BubbleBorder* border_;
 
   DISALLOW_COPY_AND_ASSIGN(BubbleBackground);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_BUBBLE_BUBBLE_BORDER_H_