cc: Expose clear and swap on Region

cc/region.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 CC_REGION_H_
 #define CC_REGION_H_
 
 #include <string>
 
 #include "base/logging.h"
 #include "cc/cc_export.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/gfx/rect.h"
 
 namespace cc {
 
 class CC_EXPORT Region {
  public:
   Region();
   Region(const Region& region);
   Region(gfx::Rect rect);
   ~Region();
 
   const Region& operator=(gfx::Rect rect);
   const Region& operator=(const Region& region);
 
+  void Swap(Region& region);
+  void Clear();
   bool IsEmpty() const;
 
   bool Contains(gfx::Point point) const;
   bool Contains(gfx::Rect rect) const;
   bool Contains(const Region& region) const;
 
   bool Intersects(gfx::Rect rect) const;
   bool Intersects(const Region& region) const;
 
   void Subtract(gfx::Rect rect);
@@ skipping 79 matching lines @@
 
 inline Region UnionRegions(const Region& a, gfx::Rect b) {
   Region result = a;
   result.Union(b);
   return result;
 }
 
 }  // namespace cc
 
 #endif  // CC_REGION_H_