Add layerTreeBuildHelper to control layer tree in ContentViewRenderView

content/browser/android/layer_tree_build_helper.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.h"
+
+#include "cc/layers/layer.h"
+#include "cc/layers/solid_color_layer.h"
+#include "content/browser/android/content_view_core_impl.h"
+
+
+namespace content {
+
+
+LayerTreeBuildHelper::LayerTreeBuildHelper()
+      : root_layer_(cc::SolidColorLayer::Create()) {
+  root_layer_->SetIsDrawable(true);
+  root_layer_->SetBackgroundColor(SK_ColorWHITE);
+}
+
+LayerTreeBuildHelper::~LayerTreeBuildHelper() {
+}
+
+cc::Layer* LayerTreeBuildHelper::GetLayerTree(
+    ContentViewCoreImpl* content_view) {

[Yaron, 2014/04/10 01:26:09]

Does this need ContentViewCoreImpl? Seems like upstream and downstream they're
both replicating the logic to handle content_view's layer. 

Can you instead get ContentView's layer, pass that into GetLayerTree as a layer
with name "content_layer_root) or something. Then, the subclass can choose that
it wants to insert the content layer somewhere insides its tree instead of
re-using as root?

[Yusuf, 2014/04/23 00:16:14]

Done.

+  if (content_view)
+    root_layer_ = content_view->GetLayer();

[Yaron, 2014/04/10 01:26:09]

I don't know if this is a real issue but if you are passed a content view once,
and then not passed a content view in a subsequent GetLayerTree, you're not
going to update and instead keep pointing back to the previous one's layer.

[Yusuf, 2014/04/23 00:16:14]

Done.

+  return root_layer_.get();
+}
+}  // namespace content