Improve Aura overdraw by changing hole calculation

ui/gfx/transform.h

 // Copyright (c) 2011 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_GFX_TRANSFORM_H_
 #define UI_GFX_TRANSFORM_H_
 #pragma once
 
 #include "third_party/skia/include/utils/SkMatrix44.h"
 #include "ui/base/ui_export.h"
@@ skipping 51 matching lines @@
   // (i.e. 'this = this * transform;').
   void PreconcatTransform(const Transform& transform);
 
   // Applies a transformation on the current transformation
   // (i.e. 'this = transform * this;').
   void ConcatTransform(const Transform& transform);
 
   // Does the transformation change anything?
   bool HasChange() const;
 
+  // Inverts the transform. Returns true if successful;
+  bool Invert();
+
   // Applies the transformation on the point. Returns true if the point is
   // transformed successfully.
   void TransformPoint(gfx::Point3f& point) const;
 
   // Applies the transformation on the point. Returns true if the point is
   // transformed successfully. Rounds the result to the nearest point.
   void TransformPoint(gfx::Point& point) const;
 
   // Applies the reverse transformation on the point. Returns true if the
   // transformation can be inverted.
@@ skipping 26 matching lines @@
                               gfx::Point3f& point) const;
 
   SkMatrix44 matrix_;
 
   // copy/assign are allowed.
 };
 
 }// namespace ui
 
 #endif  // UI_GFX_TRANSFORM_H_