Plumb native AppWindow input region through to window shape under Aura.

ui/views/widget/widget.h

 // Copyright (c) 2012 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 UI_VIEWS_WIDGET_WIDGET_H_
 #define UI_VIEWS_WIDGET_WIDGET_H_
 
 #include <set>
 #include <stack>
 #include <vector>
@@ skipping 401 matching lines @@
   void EndMoveLoop();
 
   // Places the widget in front of the specified widget in z-order.
   void StackAboveWidget(Widget* widget);
   void StackAbove(gfx::NativeView native_view);
   void StackAtTop();
 
   // Places the widget below the specified NativeView.
   void StackBelow(gfx::NativeView native_view);
 
-  // Sets a shape on the widget. This takes ownership of shape.
+  // Sets a shape on the widget. Passing a NULL |shape| reverts the widget to
+  // be rectangular. Takes ownership of |shape|.
   void SetShape(gfx::NativeRegion shape);
 
   // Hides the widget then closes it after a return to the message loop.
   virtual void Close();
 
   // TODO(beng): Move off public API.
   // Closes the widget immediately. Compare to |Close|. This will destroy the
   // window handle associated with this Widget, so should not be called from
   // any code that expects it to be valid beyond this call.
   void CloseNow();
@@ skipping 459 matching lines @@
   // True when window movement via mouse interaction with the frame should be
   // disabled.
   bool movement_disabled_;
 
   DISALLOW_COPY_AND_ASSIGN(Widget);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_WIDGET_H_