cc: Implement shared worker contexts. (v1)

ui/compositor/test/in_process_context_factory.cc

Index: ui/compositor/test/in_process_context_factory.cc
diff --git a/ui/compositor/test/in_process_context_factory.cc b/ui/compositor/test/in_process_context_factory.cc
index 942947d5b1b020f3ebfcfe21cc7cf2097d2067cb..3bb555a80aa40a2b3877bcf0ec7b08648fe5cd7f 100644
--- a/ui/compositor/test/in_process_context_factory.cc
+++ b/ui/compositor/test/in_process_context_factory.cc
@@ -115,6 +115,15 @@ void InProcessContextFactory::CreateOutputSurface(
   scoped_refptr<InProcessContextProvider> worker_context_provider =
       InProcessContextProvider::CreateOffscreen(&gpu_memory_buffer_manager_,
                                                 &image_factory_);
+  if (worker_context_provider &&
+      !worker_context_provider->BindToCurrentThread())
+    worker_context_provider = nullptr;
+  if (worker_context_provider) {
+    worker_context_provider->SetupLock();
+    // Detach from thread to allow context to be destroyed on a different
+    // thread without being used.
+    worker_context_provider->DetachFromThread();
+  }
 
   scoped_ptr<cc::OutputSurface> real_output_surface;