Stop retrieving scrolling element id from the CompositorElementId.

third_party/WebKit/Source/core/page/scrolling/ScrollState.h

 // Copyright 2015 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 ScrollState_h
 #define ScrollState_h
 
 #include <deque>
 #include <memory>
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/CoreExport.h"
+#include "core/dom/Element.h"
 #include "core/page/scrolling/ScrollStateInit.h"
 #include "platform/bindings/ScriptWrappable.h"
 #include "platform/scroll/ScrollStateData.h"
 #include "platform/wtf/Forward.h"
 
 namespace blink {
 
 class Element;
 
 class CORE_EXPORT ScrollState final
@@ skipping 42 matching lines @@
   bool shouldPropagate() const { return data_->should_propagate; };
 
   // Non web exposed methods.
   void ConsumeDeltaNative(double x, double y);
 
   // TODO(tdresser): this needs to be web exposed. See crbug.com/483091.
   void SetScrollChain(std::deque<int> scroll_chain) {
     scroll_chain_ = scroll_chain;
   }
 
-  Element* CurrentNativeScrollingElement() const;
+  Element* CurrentNativeScrollingElement();
   void SetCurrentNativeScrollingElement(Element*);
 
-  void SetCurrentNativeScrollingElementById(int element_id);
-
   bool DeltaConsumedForScrollSequence() const {
     return data_->delta_consumed_for_scroll_sequence;
   }
 
   // Scroll begin and end must propagate to all nodes to ensure
   // their state is updated.
   bool FullyConsumed() const {
     return !data_->delta_x && !data_->delta_y && !data_->is_ending &&
            !data_->is_beginning;
   }
 
   ScrollStateData* Data() const { return data_.get(); }
 
-  DEFINE_INLINE_TRACE() {}
+  DEFINE_INLINE_TRACE() { visitor->Trace(element_); }
 
  private:
   ScrollState();
   explicit ScrollState(std::unique_ptr<ScrollStateData>);
 
   std::unique_ptr<ScrollStateData> data_;
   std::deque<int> scroll_chain_;
+  Member<Element> element_;
 };
 
 }  // namespace blink
 
 #endif  // ScrollState_h