Remove non-MD code from TrayBackgroundView

ash/common/system/tray/tray_background_view.h

Index: ash/common/system/tray/tray_background_view.h
diff --git a/ash/common/system/tray/tray_background_view.h b/ash/common/system/tray/tray_background_view.h
index 49e71055e55adee2fc1244a00d2b6f4ef0d96dff..a5549cd4880690d4a14c554e2772a2e47829504a 100644
--- a/ash/common/system/tray/tray_background_view.h
+++ b/ash/common/system/tray/tray_background_view.h
@@ -81,7 +81,6 @@ class ASH_EXPORT TrayBackgroundView : public ActionableView,
   std::unique_ptr<views::InkDropRipple> CreateInkDropRipple() const override;
   std::unique_ptr<views::InkDropHighlight> CreateInkDropHighlight()
       const override;
-  void OnGestureEvent(ui::GestureEvent* event) override;
 
   // Called whenever the shelf alignment changes.
   virtual void SetShelfAlignment(ShelfAlignment alignment);
@@ -106,10 +105,8 @@ class ASH_EXPORT TrayBackgroundView : public ActionableView,
   // Sets |contents| as a child.
   void SetContents(views::View* contents);
 
-  // Creates and sets contents background to |background_|. |draws_active|
-  // determines if the view's background should be drawn as active when the view
-  // is in the active state.
-  void SetContentsBackground(bool draws_active);
+  // Creates and sets contents background to |background_|.
+  void SetContentsBackground();
 
   // Returns the bubble anchor alignment based on |shelf_alignment_|.
   views::TrayBubbleView::AnchorAlignment GetAnchorAlignment() const;
@@ -178,8 +175,8 @@ class ASH_EXPORT TrayBackgroundView : public ActionableView,
   // Owned by the view passed to SetContents().
   TrayBackground* background_;
 
-  // Determines if the view is active. This changes how the background is drawn
-  // in non-MD version and how the ink drop ripples behave in MD version.
+  // Determines if the view is active. This changes how  the ink drop ripples
+  // behave.
   bool is_active_;
 
   // Visibility of this tray's separator which is a line of 1x32px and 4px to