MacViews: Put wm window animation calls behind an interface.

ui/views/widget/native_widget_mac.h

Index: ui/views/widget/native_widget_mac.h
diff --git a/ui/views/widget/native_widget_mac.h b/ui/views/widget/native_widget_mac.h
index 2736cdc01bf3f3c5f374e71ae4aee40be14adba5..a0b678283a453b45771187c9e101fb94c44edb91 100644
--- a/ui/views/widget/native_widget_mac.h
+++ b/ui/views/widget/native_widget_mac.h
@@ -105,6 +105,7 @@ class VIEWS_EXPORT NativeWidgetMac : public internal::NativeWidgetPrivate {
       Widget::MoveLoopEscapeBehavior escape_behavior) override;
   virtual void EndMoveLoop() override;
   virtual void SetVisibilityChangedAnimationsEnabled(bool value) override;
+  virtual Widget::VisibilityAnimation* GetVisibilityAnimation() const override;
   virtual ui::NativeTheme* GetNativeTheme() const override;
   virtual void OnRootViewLayout() override;
   virtual bool IsTranslucentWindowOpacitySupported() const override;
@@ -119,7 +120,7 @@ class VIEWS_EXPORT NativeWidgetMac : public internal::NativeWidgetPrivate {
 
   internal::NativeWidgetDelegate* delegate_;
   scoped_ptr<BridgedNativeWidget> bridge_;
-
+  scoped_ptr<Widget::VisibilityAnimation> visibility_animation_;
   Widget::InitParams::Ownership ownership_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetMac);