Make the ChromeOS overview window clear its mask

ash/common/wm/overview/scoped_transform_overview_window.cc

Index: ash/common/wm/overview/scoped_transform_overview_window.cc
diff --git a/ash/common/wm/overview/scoped_transform_overview_window.cc b/ash/common/wm/overview/scoped_transform_overview_window.cc
index ca1974343fc8cc04797ae5dae6cc593286b98d7c..85ce68406e8afbea7f78a0188a6b560e030795b2 100644
--- a/ash/common/wm/overview/scoped_transform_overview_window.cc
+++ b/ash/common/wm/overview/scoped_transform_overview_window.cc
@@ -400,6 +400,7 @@ void ScopedTransformOverviewWindow::SetTransform(
   if (ash::MaterialDesignController::IsOverviewMaterial() && !mask_) {
     mask_.reset(new OverviewContentMask(
         window()->GetIntProperty(WmWindowProperty::TOP_VIEW_INSET), radius));
+    mask_->layer()->SetFillsBoundsOpaquely(false);

[varkha, 2016/07/09 11:26:13]

Brilliant, thanks for a quick tip!
The code here [1] has the same problem, right?
[1] -
https://cs.chromium.org/chromium/src/ui/views/bubble/tray_bubble_view.cc?q=Se...

     mask_->layer()->SetBounds(GetTargetBoundsInScreen());
     window()->GetLayer()->SetMaskLayer(mask_->layer());
   }