Store compositor element id in paint properties for animated objects.

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"
 
 namespace blink {
 
 TransformPaintPropertyNode* TransformPaintPropertyNode::root() {
   DEFINE_STATIC_REF(TransformPaintPropertyNode, root,
                     (TransformPaintPropertyNode::create(
                         nullptr, TransformationMatrix(), FloatPoint3D())));
   return root;
 }
 
 String TransformPaintPropertyNode::toString() const {
   return String::format(
       "parent=%p transform=%s origin=%s flattensInheritedTransform=%s "
-      "renderContextID=%x directCompositingReasons=%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());
+      compositingReasonsAsString(m_directCompositingReasons).ascii().data(),
+      m_compositorElementId.primaryId, m_compositorElementId.secondaryId);
 }
 
 }  // namespace blink