cc: Replace Region with SimpleEnclosedRegion for occlusion tracking

cc/base/simple_enclosed_region.h

Index: cc/base/simple_enclosed_region.h
diff --git a/cc/base/simple_enclosed_region.h b/cc/base/simple_enclosed_region.h
new file mode 100644
index 0000000000000000000000000000000000000000..28bec4c1575aa0f2298f2b5558afe181e61af33d
--- /dev/null
+++ b/cc/base/simple_enclosed_region.h
@@ -0,0 +1,122 @@
+// Copyright (c) 2014 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_SIMPLE_ENCLOSED_REGION_H_
+#define CC_BASE_SIMPLE_ENCLOSED_REGION_H_
+
+#include <string>
+
+#include "cc/base/cc_export.h"
+#include "ui/gfx/rect.h"
+
+namespace cc {
+
+class Region;
+
+// A constant-sized approximation of a Region. The SimpleEnclosedRegion may
+// exclude points in its approximation (may have false negatives) but will never
+// include a point that would not be in the actual Region (no false positives).
+class CC_EXPORT SimpleEnclosedRegion {
+ public:
+  SimpleEnclosedRegion() : rect_() {}
+  SimpleEnclosedRegion(const SimpleEnclosedRegion& region)
+      : rect_(region.rect_) {}
+  explicit SimpleEnclosedRegion(const gfx::Rect& rect) : rect_(rect) {}
+  SimpleEnclosedRegion(int x, int y, int w, int h) : rect_(x, y, w, h) {}
+  SimpleEnclosedRegion(int w, int h) : rect_(w, h) {}
+  explicit SimpleEnclosedRegion(const Region& region);
+  ~SimpleEnclosedRegion();
+
+  const SimpleEnclosedRegion& operator=(const gfx::Rect& rect) {
+    rect_ = rect;
+    return *this;
+  }
+  const SimpleEnclosedRegion& operator=(const SimpleEnclosedRegion& region) {
+    rect_ = region.rect_;
+    return *this;
+  }
+
+  bool IsEmpty() const { return rect_.IsEmpty(); }
+  void Clear() { rect_ = gfx::Rect(); }
+  size_t GetRegionComplexity() const { return rect_.IsEmpty() ? 0 : 1; }
+
+  bool Contains(const gfx::Point& point) const { return rect_.Contains(point); }
+  bool Contains(const gfx::Rect& rect) const { return rect_.Contains(rect); }
+  bool Contains(const SimpleEnclosedRegion& region) const {
+    return rect_.Contains(region.rect_);
+  }
+
+  bool Intersects(const gfx::Rect& rect) const {
+    return rect_.Intersects(rect);
+  }
+  bool Intersects(const SimpleEnclosedRegion& region) const {
+    return rect_.Intersects(region.rect_);
+  }
+
+  void Subtract(const gfx::Rect& sub_rect);
+  void Subtract(const SimpleEnclosedRegion& sub_region) {
+    Subtract(sub_region.rect_);
+  }
+  void Union(const gfx::Rect& new_rect);
+  void Union(const SimpleEnclosedRegion& new_region) {
+    Union(new_region.rect_);
+  }
+  void Intersect(const gfx::Rect& in_rect) { return rect_.Intersect(in_rect); }
+  void Intersect(const SimpleEnclosedRegion& in_region) {
+    Intersect(in_region.rect_);
+  }
+
+  bool Equals(const SimpleEnclosedRegion& other) const {
+    bool both_empty = rect_.IsEmpty() && other.rect_.IsEmpty();
+    return both_empty || rect_ == other.rect_;
+  }
+
+  gfx::Rect bounds() const { return rect_; }
+
+  // The value of |i| must be less than GetRegionComplexity().
+  gfx::Rect GetRect(size_t i) const;
+
+  std::string ToString() const { return rect_.ToString(); }
+
+ private:
+  gfx::Rect rect_;
+};
+
+inline bool operator==(const SimpleEnclosedRegion& a,
+                       const SimpleEnclosedRegion& b) {
+  return a.Equals(b);
+}
+
+inline bool operator!=(const SimpleEnclosedRegion& a,
+                       const SimpleEnclosedRegion& b) {
+  return !(a == b);
+}
+
+inline SimpleEnclosedRegion SubtractSimpleEnclosedRegions(
+    const SimpleEnclosedRegion& a,
+    const SimpleEnclosedRegion& b) {
+  SimpleEnclosedRegion result = a;
+  result.Subtract(b);
+  return result;
+}
+
+inline SimpleEnclosedRegion IntersectSimpleEnclosedRegions(
+    const SimpleEnclosedRegion& a,
+    const SimpleEnclosedRegion& b) {
+  SimpleEnclosedRegion result = a;
+  result.Intersect(b);
+  return result;
+}
+
+inline SimpleEnclosedRegion UnionSimpleEnclosedRegions(
+    const SimpleEnclosedRegion& a,
+    const SimpleEnclosedRegion& b) {
+  SimpleEnclosedRegion result = a;
+  result.Union(b);
+  return result;
+}
+
+}  // namespace cc
+
+#endif  // CC_BASE_SIMPLE_ENCLOSED_REGION_H_