Replace Ash web notification tray view with a button.

ash/system/tray/tray_background_view.h

Index: ash/system/tray/tray_background_view.h
diff --git a/ash/system/tray/tray_background_view.h b/ash/system/tray/tray_background_view.h
index 20a70311fff60c1040767b73d0c62c348dbdf02b..4c25ee8145194c4cfa2676420c3e414dff5ee799 100644
--- a/ash/system/tray/tray_background_view.h
+++ b/ash/system/tray/tray_background_view.h
@@ -56,7 +56,8 @@ class ASH_EXPORT TrayBackgroundView : public internal::ActionableView,
     DISALLOW_COPY_AND_ASSIGN(TrayContainer);
   };
 
-  explicit TrayBackgroundView(internal::StatusAreaWidget* status_area_widget);
+  TrayBackgroundView(internal::StatusAreaWidget* status_area_widget,
+                              bool set_background);

[tfarina, 2012/08/26 22:17:59]

nit: fix indentation here.

   virtual ~TrayBackgroundView();
 
   // Called after the tray has been added to the widget containing it.
@@ -84,8 +85,9 @@ class ASH_EXPORT TrayBackgroundView : public internal::ActionableView,
 
   virtual string16 GetAccessibleName() = 0;
 
-  // Sets |contents| as a child and sets its background to |background_|.
-  void SetContents(views::View* contents);
+  // Sets |contents| as a child. If |set_background| is true, also creates and
+  // sets |background_|.
+  void SetContents(views::View* contents, bool set_background);
 
   // Sets whether the tray paints a background. Default is true, but is set to
   // false if a window overlaps the shelf.