cc : Clean up cc clip tree

cc/trees/property_tree.h

Index: cc/trees/property_tree.h
diff --git a/cc/trees/property_tree.h b/cc/trees/property_tree.h
index 8c9d158a7bc28ee99741741d115eba725fbe0505..98c2c71fc00afb5d289294c680856ee7d32a530c 100644
--- a/cc/trees/property_tree.h
+++ b/cc/trees/property_tree.h
@@ -548,6 +548,18 @@ struct DrawTransformData {
         transforms(gfx::Transform(), gfx::Transform()) {}
 };
 
+struct ConditionalClip {
+  bool is_clipped;
+  gfx::RectF clip_rect;
+};
+
+struct ClipRectData {
+  int target_id;
+  ConditionalClip clip;
+
+  ClipRectData() : target_id(-1) {}
+};
+
 struct PropertyTreesCachedData {
   int transform_tree_update_number;
   std::vector<AnimationScaleData> animation_scales;
@@ -654,6 +666,8 @@ class CC_EXPORT PropertyTrees final {
       int transform_id,
       int effect_id) const;
 
+  ClipRectData& FetchClipRectFromCache(int clip_id, int target_id);
+
  private:
   gfx::Vector2dF inner_viewport_container_bounds_delta_;
   gfx::Vector2dF outer_viewport_container_bounds_delta_;