(not for commit) Create 2nd ContextProvider for Ganesh rasterization.

content/renderer/gpu/mailbox_output_surface.h

Index: content/renderer/gpu/mailbox_output_surface.h
diff --git a/content/renderer/gpu/mailbox_output_surface.h b/content/renderer/gpu/mailbox_output_surface.h
index 1480af3220d30f2379b504a6cc3b5fadfefeed4c..098b9a9873f96e50e81013106c15699cc3a01dbc 100644
--- a/content/renderer/gpu/mailbox_output_surface.h
+++ b/content/renderer/gpu/mailbox_output_surface.h
@@ -30,6 +30,8 @@ class MailboxOutputSurface : public CompositorOutputSurface {
       int32 routing_id,
       uint32 output_surface_id,
       const scoped_refptr<ContextProviderCommandBuffer>& context_provider,
+      const scoped_refptr<ContextProviderCommandBuffer>&
+          worker_context_provider,
       scoped_ptr<cc::SoftwareOutputDevice> software_device,
       scoped_refptr<FrameSwapMessageQueue> swap_frame_message_queue,
       cc::ResourceFormat format);