Rewrite blink->cc scroll offset logic for SPV2

third_party/WebKit/Source/platform/graphics/compositing/PropertyTreeManager.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 PropertyTreeManager_h
 #define PropertyTreeManager_h
 
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/Noncopyable.h"
@@ skipping 57 matching lines @@
   // platform/graphics/paint/README.md for more.
   //
   // With the above as background, we can now state more clearly a description
   // of the below set of compositor node methods: they take Blink paint property
   // tree nodes as input, create a corresponding compositor property tree node
   // if none yet exists, and return the compositor node's 'node id', a.k.a.,
   // 'node index'.
 
   int ensureCompositorTransformNode(const TransformPaintPropertyNode*);
   int ensureCompositorClipNode(const ClipPaintPropertyNode*);
+  // If a new compositor scroll node is created, this also handles updating
+  // the associated compositor transform node's scroll properties. Blink's
+  // transform nodes are used for scroll offset whereas cc's transform nodes
+  // store the scroll offset in a separate field.
   int ensureCompositorScrollNode(const ScrollPaintPropertyNode*);
 
   int switchToEffectNode(const EffectPaintPropertyNode& nextEffect);
   int getCurrentCompositorEffectNodeIndex() const {
     return m_effectStack.back().id;
   }
 
-  // Scroll offset has special treatment in the transform and scroll trees.
-  void updateScrollOffset(int layerId, int scrollId);
-
  private:
   void buildEffectNodesRecursively(const EffectPaintPropertyNode* nextEffect);
 
   cc::TransformTree& transformTree();
   cc::ClipTree& clipTree();
   cc::EffectTree& effectTree();
   cc::ScrollTree& scrollTree();
 
   const EffectPaintPropertyNode* currentEffectNode() const;
 
@@ skipping 18 matching lines @@
   Vector<BlinkEffectAndCcIdPair> m_effectStack;
 
 #if DCHECK_IS_ON()
   HashSet<const EffectPaintPropertyNode*> m_effectNodesConverted;
 #endif
 };
 
 }  // namespace blink
 
 #endif  // PropertyTreeManager_h