[compositor-worker] root scrolling layer is associated with document scrolling element

third_party/WebKit/Source/platform/graphics/CompositorMutableStateProvider.h

 // Copyright 2016 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 CompositorMutableStateProvider_h
 #define CompositorMutableStateProvider_h
 
 #include "platform/PlatformExport.h"
 #include <cstdint>
 #include <memory>
 
 namespace cc {
 class LayerTreeImpl;
 }  // namespace cc
 
 namespace blink {
 
 class CompositorMutableState;
 struct CompositorMutations;
 
 // This class is a window onto compositor-owned state. It vends out wrappers
 // around per-element bits of this state.
 class PLATFORM_EXPORT CompositorMutableStateProvider {
  public:
   CompositorMutableStateProvider(cc::LayerTreeImpl*, CompositorMutations*);
   ~CompositorMutableStateProvider();
 
   std::unique_ptr<CompositorMutableState> getMutableStateFor(
-      uint64_t elementId);
+      uint64_t elementId,
+      uint64_t scrollingElementId);
 
  private:
   cc::LayerTreeImpl* m_tree;
   CompositorMutations* m_mutations;
 };
 
 }  // namespace blink
 
 #endif  // CompositorMutableStateProvider_h