Move scroll paint property nodes to be owned by the transform tree

third_party/WebKit/Source/platform/graphics/paint/TransformPaintPropertyNode.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/TransformPaintPropertyNode.h"
 
 #include "platform/graphics/paint/PropertyTreeState.h"
 
 namespace blink {
 
 TransformPaintPropertyNode* TransformPaintPropertyNode::root() {
   DEFINE_STATIC_REF(TransformPaintPropertyNode, root,
                     (TransformPaintPropertyNode::create(
                         nullptr, TransformationMatrix(), FloatPoint3D(),
                         ScrollPaintPropertyNode::root())));
   return root;
 }
 
-// TODO(pdr): print out scroll node information.
 String TransformPaintPropertyNode::toString() const {
-  return String::format(
+  auto transform = String::format(
       "parent=%p transform=%s origin=%s flattensInheritedTransform=%s "
       "renderingContextId=%x directCompositingReasons=%s "
       "compositorElementId=(%d, %d)",
       m_parent.get(), m_matrix.toString().ascii().data(),
       m_origin.toString().ascii().data(),
       m_flattensInheritedTransform ? "yes" : "no", m_renderingContextId,
       compositingReasonsAsString(m_directCompositingReasons).ascii().data(),
       m_compositorElementId.primaryId, m_compositorElementId.secondaryId);
+  if (m_scroll)
+    return transform + " scroll=" + m_scroll->toString();
+  return transform;
 }
 
 #if DCHECK_IS_ON()
 
 String TransformPaintPropertyNode::toTreeString() const {
   return blink::PropertyTreeStatePrinter<blink::TransformPaintPropertyNode>()
       .pathAsString(this);
 }
 
 #endif
 
 }  // namespace blink