Improve Aura overdraw by changing hole calculation

ui/gfx/transform.cc

 // 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.
 
 #include "ui/gfx/transform.h"
 #include "ui/gfx/point3.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/skia_util.h"
 
 namespace {
@@ skipping 84 matching lines @@
 void Transform::ConcatTransform(const Transform& transform) {
   if (!transform.matrix_.isIdentity()) {
     matrix_.postConcat(transform.matrix_);
   }
 }
 
 bool Transform::HasChange() const {
   return !matrix_.isIdentity();
 }
 
+bool Transform::Invert() {
+  return matrix_.invert(&matrix_);
+}
+
 void Transform::TransformPoint(gfx::Point& point) const {
   TransformPointInternal(matrix_, point);
 }
 
 void Transform::TransformPoint(gfx::Point3f& point) const {
   TransformPointInternal(matrix_, point);
 }
 
 bool Transform::TransformPointReverse(gfx::Point& point) const {
   // TODO(sad): Try to avoid trying to invert the matrix.
@@ skipping 58 matching lines @@
     0,
     1 };
 
   xform.map(p);
 
   point.SetPoint(SymmetricRound(p[0]),
                  SymmetricRound(p[1]));
 }
 
 }  // namespace ui