Add toString() for paint property node classes

third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.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/ScrollPaintPropertyNode.h"
 
 namespace blink {
 
 ScrollPaintPropertyNode* ScrollPaintPropertyNode::root() {
   DEFINE_STATIC_REF(ScrollPaintPropertyNode, root,
                     (ScrollPaintPropertyNode::create(
                         nullptr, TransformPaintPropertyNode::root(), IntSize(),
                         IntSize(), false, false, 0)));
   return root;
 }
 
+String ScrollPaintPropertyNode::toString() const {
+  FloatSize scrollOffset =
+      m_scrollOffsetTranslation->matrix().to2DTranslation();
+  std::string mainThreadScrollingReasonsAsText =
+      MainThreadScrollingReason::mainThreadScrollingReasonsAsText(
+          m_mainThreadScrollingReasons);
+  return String::format(
+      "scrollOffsetTranslation=%s clip=%s bounds=%s "
+      "mainThreadScrollingReasons=%s",
+      scrollOffset.toString().ascii().data(), m_clip.toString().ascii().data(),
+      m_bounds.toString().ascii().data(),
+      mainThreadScrollingReasonsAsText.c_str());
+}
+
 }  // namespace blink