Add ScrollTree::FindNodeFromElementId

cc/trees/property_tree.h

 // Copyright 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_TREES_PROPERTY_TREE_H_
 #define CC_TREES_PROPERTY_TREE_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 486 matching lines @@
                           LayerTreeImpl* layer_tree_impl);
   gfx::ScrollOffset ClampScrollOffsetToLimits(gfx::ScrollOffset offset,
                                               ScrollNode* scroll_node) const;
 
   const SyncedScrollOffset* GetSyncedScrollOffset(int layer_id) const;
 
 #if DCHECK_IS_ON()
   void CopyCompleteTreeState(const ScrollTree& other);
 #endif
 
+  ScrollNode* FindNodeFromElementId(ElementId id);
+
  private:
   using ScrollOffsetMap = std::unordered_map<int, gfx::ScrollOffset>;
   using SyncedScrollOffsetMap =
       std::unordered_map<int, scoped_refptr<SyncedScrollOffset>>;
 
   int currently_scrolling_node_id_;
 
   // On the main thread we store the scroll offsets directly since the main
   // thread only needs to keep track of the current main thread state. The impl
   // thread stores a map of SyncedProperty instances in order to track
@@ skipping 212 matching lines @@
   DrawTransforms& GetDrawTransforms(int transform_id, int effect_id) const;
   DrawTransformData& FetchDrawTransformsDataFromCache(int transform_id,
                                                       int effect_id) const;
 
   PropertyTreesCachedData cached_data_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_PROPERTY_TREE_H_