[SPv2] Add CSS mix-blend-mode support

third_party/WebKit/Source/platform/graphics/paint/EffectPaintPropertyNode.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/EffectPaintPropertyNode.h"
 
 namespace blink {
 
 EffectPaintPropertyNode* EffectPaintPropertyNode::root() {
   DEFINE_STATIC_REF(
       EffectPaintPropertyNode, root,
       (EffectPaintPropertyNode::create(
           nullptr, TransformPaintPropertyNode::root(),
-          ClipPaintPropertyNode::root(), CompositorFilterOperations(), 1.0)));
+          ClipPaintPropertyNode::root(), CompositorFilterOperations(), 1.0,
+          SkBlendMode::kSrcOver)));
   return root;
 }
 
 cc::Layer* EffectPaintPropertyNode::ensureDummyLayer() const {
   if (m_dummyLayer)
     return m_dummyLayer.get();
   m_dummyLayer = cc::Layer::Create();
   return m_dummyLayer.get();
 }
 
 String EffectPaintPropertyNode::toString() const {
   return String::format(
       "localTransformSpace=%p outputClip=%p opacity=%f filter=%s",
       m_localTransformSpace.get(), m_outputClip.get(), m_opacity,
       m_filter.toString().ascii().data());
 }
 
 }  // namespace blink