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..be32a54f559fba87813d8cde2e9ce34e2ad1dba2 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -124,6 +124,8 @@ bool LayerTreeHost::InitializeProxy(scoped_ptr<Proxy> proxy) {
   if (!output_surface)
     return false;
 
+  using_software_renderer_ = !output_surface->context3d();

[danakj, 2013/06/26 19:09:57]

This would be wrong on WebView when they defer initialization of GL until later
on. They'd end up with a GLRenderer, but getting software WebGL stuff. Maybe
that's okay though?

[boliu, 2013/06/28 01:27:29]

For android webview, we should strive to make GL mode always work correctly at
the expense of software mode. So this condition should be

!output_surface->context3d() &&
!output_surface->capabilities().deferred_gl_initialization

There is the caveat that context3d() may always be null even if
using_software_renderer_ is false, but I don't think any null checks are needed
in this patch. I think the actual usage of the mailbox resource is in
TextureLayerImpl only, which is skipped in webview software mode already.

+
   proxy_ = proxy.Pass();
   proxy_->Start(output_surface.Pass());
   return true;
@@ -707,6 +709,10 @@ void LayerTreeHost::IncrementLCDTextMetrics(
   }
 }
 
+bool LayerTreeHost::UsingSoftwareRenderer() {
+  return using_software_renderer_;
+}
+
 void LayerTreeHost::UpdateLayers(Layer* root_layer,
                                  ResourceUpdateQueue* queue) {
   TRACE_EVENT1("cc", "LayerTreeHost::UpdateLayers",