Fix accessability for web notification tray.

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 61b3e42a9052a75fdb8d446589992bb66e3d28c2..20a70311fff60c1040767b73d0c62c348dbdf02b 100644
--- a/ash/system/tray/tray_background_view.h
+++ b/ash/system/tray/tray_background_view.h
@@ -67,6 +67,7 @@ class ASH_EXPORT TrayBackgroundView : public internal::ActionableView,
   virtual void OnMouseExited(const ui::MouseEvent& event) OVERRIDE;
   virtual void ChildPreferredSizeChanged(views::View* child) OVERRIDE;
   virtual void OnPaintFocusBorder(gfx::Canvas* canvas) OVERRIDE;
+  virtual void GetAccessibleState(ui::AccessibleViewState* state) OVERRIDE;
   virtual void AboutToRequestFocusFromTabTraversal(bool reverse) OVERRIDE;
 
   // Overridden from internal::ActionableView.
@@ -81,6 +82,8 @@ class ASH_EXPORT TrayBackgroundView : public internal::ActionableView,
   // Called when the anchor (tray or bubble) may have moved or changed.
   virtual void AnchorUpdated() {}
 
+  virtual string16 GetAccessibleName() = 0;
+
   // Sets |contents| as a child and sets its background to |background_|.
   void SetContents(views::View* contents);