Make scroll translation transform nodes reference scroll nodes

third_party/WebKit/Source/platform/graphics/paint/PropertyTreeState.cpp

 // 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.
 
 #include "platform/graphics/paint/PropertyTreeState.h"
 
 #include "platform/graphics/paint/GeometryMapper.h"
 
 namespace blink {
 
@@ skipping 12 matching lines @@
 
 template <typename PropertyNode>
 bool isAncestorOf(const PropertyNode* ancestor, const PropertyNode* child) {
   while (child && child != ancestor) {
     child = child->parent();
   }
   return child == ancestor;
 }
 
 const CompositorElementId PropertyTreeState::compositorElementId() const {
-// Zero or more of the scroll, effect or transform nodes could have a
-// compositor element id. The order doesn't matter as the element id should be
-// the same on all that have a non-default CompositorElementId.
+// The effect or transform nodes could have a compositor element id. The order
+// doesn't matter as the element id should be the same on all that have a
+// non-default CompositorElementId.
 #if DCHECK_IS_ON()
   CompositorElementId expectedElementId;
   if (CompositorElementId actualElementId = effect()->compositorElementId()) {
     expectedElementId = actualElementId;
   }
-  if (CompositorElementId actualElementId = scroll()->compositorElementId()) {
-    if (!expectedElementId)
-      expectedElementId = actualElementId;
-    else
-      DCHECK_EQ(expectedElementId, actualElementId);
-  }
   if (CompositorElementId actualElementId =
           transform()->compositorElementId()) {
     if (expectedElementId)
       DCHECK_EQ(expectedElementId, actualElementId);
   }
 #endif
   if (effect()->compositorElementId())
     return effect()->compositorElementId();
-  if (scroll()->compositorElementId())
-    return scroll()->compositorElementId();
   if (transform()->compositorElementId())
     return transform()->compositorElementId();
   return CompositorElementId();
 }
 
 PropertyTreeState::InnermostNode PropertyTreeState::innermostNode() const {
   // TODO(chrishtr): this is very inefficient when innermostNode() is called
   // repeatedly.
   bool clipTransformStrictAncestorOfTransform =
       m_clip->localTransformSpace() != m_transform.get() &&
@@ skipping 39 matching lines @@
 #if DCHECK_IS_ON()
 
 String PropertyTreeState::toTreeString() const {
   return transform()->toTreeString() + "\n" + clip()->toTreeString() + "\n" +
          effect()->toTreeString() + "\n" + scroll()->toTreeString();
 }
 
 #endif
 
 }  // namespace blink