cc: Replace Region with SimpleEnclosedRegion for occlusion tracking

cc/base/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_BASE_REGION_H_
 #define CC_BASE_REGION_H_
 
 #include <string>
 
-#include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/skia_util.h"
 
 namespace base {
 class Value;
 namespace debug {
 class TracedValue;
 }
 }
 
 namespace cc {
+class SimpleEnclosedRegion;
 
 class CC_EXPORT Region {
  public:
   Region();
   Region(const Region& region);
   Region(const gfx::Rect& rect);  // NOLINT(runtime/explicit)
   ~Region();
 
   const Region& operator=(const gfx::Rect& rect);
   const Region& operator=(const Region& region);
 
   void Swap(Region* region);
   void Clear();
   bool IsEmpty() const;
   int GetRegionComplexity() const;
 
   bool Contains(const gfx::Point& point) const;
   bool Contains(const gfx::Rect& rect) const;
   bool Contains(const Region& region) const;
 
   bool Intersects(const gfx::Rect& rect) const;
   bool Intersects(const Region& region) const;
 
   void Subtract(const gfx::Rect& rect);
   void Subtract(const Region& region);
+  void Subtract(const SimpleEnclosedRegion& region);
   void Union(const gfx::Rect& rect);
   void Union(const Region& region);
   void Intersect(const gfx::Rect& rect);
   void Intersect(const Region& region);
 
   bool Equals(const Region& other) const {
     return skregion_ == other.skregion_;
   }
 
   gfx::Rect bounds() const {
@@ skipping 70 matching lines @@
 
 inline Region UnionRegions(const Region& a, const gfx::Rect& b) {
   Region result = a;
   result.Union(b);
   return result;
 }
 
 }  // namespace cc
 
 #endif  // CC_BASE_REGION_H_