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 8d93426f32ea842a2d7d437efc3905d12adae566..37fd5783294939dc0240ee4c04ab9f5ef38b2be4 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -123,6 +123,10 @@ bool LayerTreeHost::InitializeProxy(scoped_ptr<Proxy> proxy) {
   if (!output_surface)
     return false;
 
+  using_gl_renderer_ =
+      output_surface->context3d() ||
+      output_surface->capabilities().deferred_gl_initialization;

[piman, 2013/07/02 04:00:09]

Note: during the lifetime of the LTH, we may recreate the OutputSurface after a
lost context - see e.g. ThreadProxy::DoCreateAndInitializeOutputSurface()

I think it will happen that a recreated output surface will have a different
type than the one created at the beginning, e.g. if we completely lost the GPU
context and we're blacklisted for the session, and we want to fallback to
software. Even if not now, that's something we want to be able to do eventually.

Based on that, maybe what's best to do is to keep this flag on the
RendererCapabilities, and it should flow naturally to the LTH before the first
commit on that new surface - maybe renamed as "using_shared_memory_resources" or
something.

[jbauman, 2013/07/02 20:16:19]

Ok, I'm now passing it through RendererCapabilities instead.

+
   proxy_ = proxy.Pass();
   proxy_->Start(output_surface.Pass());
   return true;
@@ -682,6 +686,8 @@ void LayerTreeHost::CalculateLCDTextMetricsCallback(Layer* layer) {
   }
 }
 
+bool LayerTreeHost::UsingGLRenderer() { return using_gl_renderer_; }
+
 void LayerTreeHost::UpdateLayers(Layer* root_layer,
                                  ResourceUpdateQueue* queue) {
   TRACE_EVENT1("cc", "LayerTreeHost::UpdateLayers",