Add ink drop masking to TrayBackgroundView

ui/views/animation/ink_drop_impl.h

Index: ui/views/animation/ink_drop_impl.h
diff --git a/ui/views/animation/ink_drop_impl.h b/ui/views/animation/ink_drop_impl.h
index 698e44c9634194bc85f1ffa2148751a63880665a..961f80b0cfbd37373bf8bced5f2e82e2b95ade4e 100644
--- a/ui/views/animation/ink_drop_impl.h
+++ b/ui/views/animation/ink_drop_impl.h
@@ -45,11 +45,11 @@ class VIEWS_EXPORT InkDropImpl : public InkDrop,
   };
 
   // Constructs an ink drop that will attach the ink drop to the given
-  // |ink_drop_host|.
+  // |ink_drop_host|. |host_size| is used to set the size of the ink drop layer.
   //
   // By default the highlight will be made visible while |this| is hovered but
   // not focused and the NONE AutoHighlightMode will be used.
-  explicit InkDropImpl(InkDropHost* ink_drop_host);
+  InkDropImpl(InkDropHost* ink_drop_host, const gfx::Size& host_size);
   ~InkDropImpl() override;
 
   void SetShowHighlightOnHover(bool show_highlight_on_hover);
@@ -66,6 +66,7 @@ class VIEWS_EXPORT InkDropImpl : public InkDrop,
   void SetAutoHighlightMode(AutoHighlightMode auto_highlight_mode);
 
   // InkDrop:
+  void HostSizeChanged(const gfx::Size& new_size) override;
   InkDropState GetTargetInkDropState() const override;
   void AnimateToState(InkDropState ink_drop_state) override;
   void SnapToActivated() override;