Add toString() for paint property node classes

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 "transform=" + m_matrix.toString() + " origin=" + m_origin.toString();
+}
+
 }  // namespace blink