MacViews: Put wm window animation calls behind an interface.

ui/views/widget/widget.cc

Index: ui/views/widget/widget.cc
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index 8cf11ffafca333f00ce45e83ad71ae5ff49816bb..84e32915ddb77bb27d93aa515a0259d35b241d67 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -519,6 +519,10 @@ void Widget::SetVisibilityChangedAnimationsEnabled(bool value) {
   native_widget_->SetVisibilityChangedAnimationsEnabled(value);
 }
 
+Widget::VisibilityAnimation* Widget::GetVisibilityAnimation() const {
+  return native_widget_->GetVisibilityAnimation();
+}
+
 Widget::MoveLoopResult Widget::RunMoveLoop(
     const gfx::Vector2d& drag_offset,
     MoveLoopSource source,