MacViews: Put wm window animation calls behind an interface.

ui/views/widget/native_widget_aura.h

Index: ui/views/widget/native_widget_aura.h
diff --git a/ui/views/widget/native_widget_aura.h b/ui/views/widget/native_widget_aura.h
index bdd92e4c0afa792ca911c7dbaa0e106f4b4c7287..f503712dd7383470c46241035cf1af5d79911b77 100644
--- a/ui/views/widget/native_widget_aura.h
+++ b/ui/views/widget/native_widget_aura.h
@@ -129,6 +129,7 @@ class VIEWS_EXPORT NativeWidgetAura
       Widget::MoveLoopEscapeBehavior escape_behavior) override;
   void EndMoveLoop() override;
   void SetVisibilityChangedAnimationsEnabled(bool value) override;
+  Widget::VisibilityAnimation* GetVisibilityAnimation() const override;
   ui::NativeTheme* GetNativeTheme() const override;
   void OnRootViewLayout() override;
   bool IsTranslucentWindowOpacitySupported() const override;
@@ -223,6 +224,8 @@ class VIEWS_EXPORT NativeWidgetAura
   scoped_ptr<DropHelper> drop_helper_;
   int last_drop_operation_;
 
+  scoped_ptr<Widget::VisibilityAnimation> visibility_animation_;
+
   // The following factory is used for calls to close the NativeWidgetAura
   // instance.
   base::WeakPtrFactory<NativeWidgetAura> close_widget_factory_;