[ash-md] Fixes a bug with setting window shape to mask header in overview

ash/common/wm/overview/scoped_transform_overview_window.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_COMMON_WM_OVERVIEW_SCOPED_TRANSFORM_OVERVIEW_WINDOW_H_
 #define ASH_COMMON_WM_OVERVIEW_SCOPED_TRANSFORM_OVERVIEW_WINDOW_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 122 matching lines @@
 
   // A weak pointer to the real window in the overview.
   WmWindow* window_;
 
   // Mask layer that hides the original window header.
   std::unique_ptr<OverviewContentMask> mask_;
 
   // Original window shape, if it was set on a window.
   std::unique_ptr<SkRegion> original_window_shape_;
 
+  // True after the |original_window_shape_| has been set or after it has
+  // been determined that window shape was not originally set on the |window_|.
+  bool determined_original_window_shape_;
+
   // If true, the window was minimized and should be restored if the window
   // was not selected.
   bool minimized_;
 
   // Tracks if this window was ignored by the shelf.
   bool ignored_by_shelf_;
 
   // True if the window has been transformed for overview mode.
   bool overview_started_;
 
   // The original transform of the window before entering overview mode.
   gfx::Transform original_transform_;
 
   // Keeps track of the original transform used when |this| has been positioned
   // during SelectorItem layout.
   gfx::Transform overview_transform_;
 
   // The original opacity of the window before entering overview mode.
   float original_opacity_;
 
   base::WeakPtrFactory<ScopedTransformOverviewWindow> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedTransformOverviewWindow);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_OVERVIEW_SCOPED_TRANSFORM_OVERVIEW_WINDOW_H_