cc: Implement tiling iterator based on pyramid sequence.

cc/base/index_rect.h

Index: cc/base/index_rect.h
diff --git a/cc/base/index_rect.h b/cc/base/index_rect.h
index d6d2d917828b33d4f2a8b7169c1e7a8b61d4b8c2..cc8deedb2e4d7f6e7838d6faa9de5ceecf5fa5ab 100644
--- a/cc/base/index_rect.h
+++ b/cc/base/index_rect.h
@@ -100,6 +100,9 @@ class CC_EXPORT IndexRect {
   // inside this index rectangle, including edge indices.
   bool Contains(int index_x, int index_y) const;
 
+  // Shrink the index rect by the specified amount on each side.
+  void Inset(int left, int right, int top, int bottom);
+
   std::string ToString() const;
 
  private: