Add layerTreeBuildHelper to control layer tree in ContentViewRenderView

content/browser/android/layer_tree_build_helper_impl.cc

+// Copyright 2014 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 "content/browser/android/layer_tree_build_helper_impl.h"
+
+#include "cc/layers/layer.h"
+#include "cc/layers/solid_color_layer.h"
+
+namespace content {
+
+LayerTreeBuildHelperImpl::LayerTreeBuildHelperImpl() {
+  root_layer_ = cc::SolidColorLayer::Create();
+  root_layer_->SetIsDrawable(true);
+  root_layer_->SetBackgroundColor(SK_ColorWHITE);
+}
+
+LayerTreeBuildHelperImpl::~LayerTreeBuildHelperImpl() {
+}
+
+scoped_refptr<cc::Layer> LayerTreeBuildHelperImpl::GetLayerTree(
+    scoped_refptr<cc::Layer> content_root_layer) {
+  if (content_root_layer)
+    root_layer_ = content_root_layer;
+  else
+    root_layer_ = cc::Layer::Create();
+
+  return root_layer_;
+}
+}  // namespace content