Allow WebExternalTextureLayers to receive a bitmap along with a mailbox

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 5e19eb3eb3c8acb70f68dba1d64863f6bb806297..d5713b8e95faed5aadbe9c36e7ceb4e8cd5aaccb 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -124,6 +124,10 @@ bool LayerTreeHost::InitializeProxy(scoped_ptr<Proxy> proxy) {
   if (!output_surface)
     return false;
 
+  using_gl_renderer_ =
+      output_surface->context3d() ||
+      output_surface->capabilities().deferred_gl_initialization;
+
   proxy_ = proxy.Pass();
   proxy_->Start(output_surface.Pass());
   return true;
@@ -707,6 +711,8 @@ void LayerTreeHost::IncrementLCDTextMetrics(
   }
 }
 
+bool LayerTreeHost::UsingGLRenderer() { return using_gl_renderer_; }
+
 void LayerTreeHost::UpdateLayers(Layer* root_layer,
                                  ResourceUpdateQueue* queue) {
   TRACE_EVENT1("cc", "LayerTreeHost::UpdateLayers",