app_list: Fix shadow bleeds over launcher button and steals mouse events

ui/views/widget/widget_delegate.h

Index: ui/views/widget/widget_delegate.h
diff --git a/ui/views/widget/widget_delegate.h b/ui/views/widget/widget_delegate.h
index 3239c1d75e7ef378836c6208abacb18b9f613b3b..c92c81c8c8c6ecadbded7d8141bc75723ea35403 100644
--- a/ui/views/widget/widget_delegate.h
+++ b/ui/views/widget/widget_delegate.h
@@ -146,6 +146,12 @@ class VIEWS_EXPORT WidgetDelegate {
   // manage the positions by ourselves.
   virtual bool WillProcessWorkAreaChange() const;
 
+  // Returns true if window has a hit-test mask.
+  virtual bool HasHitTestMask() const;
+
+  // Provides the hit-test mask if HasHitTestMask above returns true.
+  virtual void GetHitTestMask(gfx::Path* mask) const;
+
  protected:
   virtual ~WidgetDelegate() {}