Implement interest rects for synchronized paint.

third_party/WebKit/Source/platform/geometry/IntRect.h

Index: third_party/WebKit/Source/platform/geometry/IntRect.h
diff --git a/third_party/WebKit/Source/platform/geometry/IntRect.h b/third_party/WebKit/Source/platform/geometry/IntRect.h
index 70f5a9a3321aa24250b8b0eec2e7f36d22bed623..e06105496fe807484006a6783496858be08623ff 100644
--- a/third_party/WebKit/Source/platform/geometry/IntRect.h
+++ b/third_party/WebKit/Source/platform/geometry/IntRect.h
@@ -27,6 +27,7 @@
 #define IntRect_h
 
 #include "platform/geometry/IntPoint.h"
+#include "platform/geometry/IntRectOutsets.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/Vector.h"
 #include "wtf/VectorTraits.h"
@@ -89,6 +90,12 @@ public:
 
     void expand(const IntSize& size) { m_size += size; }
     void expand(int dw, int dh) { m_size.expand(dw, dh); }
+    void expand(const IntRectOutsets& outsets)
+    {
+        m_location.move(-outsets.left(), -outsets.top());
+        m_size.expand(outsets.left() + outsets.right(), outsets.top() + outsets.bottom());
+    }
+
     void contract(const IntSize& size) { m_size -= size; }
     void contract(int dw, int dh) { m_size.expand(-dw, -dh); }