Defer compositor context creation to the thread.

cc/output/output_surface.h

Index: cc/output/output_surface.h
diff --git a/cc/output/output_surface.h b/cc/output/output_surface.h
index 326b2fd2fbf22e8f3ff832b208c4a316c744a583..701fbcc21b3b640804a8b5080ae17a94747770f8 100644
--- a/cc/output/output_surface.h
+++ b/cc/output/output_surface.h
@@ -46,17 +46,21 @@ class OutputSurfaceClient;
 //      surface (on the compositor thread) and go back to step 1.
 class CC_EXPORT OutputSurface : public base::trace_event::MemoryDumpProvider {
  public:
-  OutputSurface(scoped_refptr<ContextProvider> context_provider,
-                scoped_refptr<ContextProvider> worker_context_provider,
-                scoped_refptr<VulkanContextProvider> vulkan_context_provider,
-                std::unique_ptr<SoftwareOutputDevice> software_device);
-  OutputSurface(scoped_refptr<ContextProvider> context_provider,
-                scoped_refptr<ContextProvider> worker_context_provider);
-  explicit OutputSurface(scoped_refptr<ContextProvider> context_provider);
+  OutputSurface(
+      std::unique_ptr<ContextProvider::Factory> compositor_context_factory,
+      scoped_refptr<ContextProvider> worker_context_provider,
+      scoped_refptr<VulkanContextProvider> vulkan_context_provider,
+      std::unique_ptr<SoftwareOutputDevice> software_device);
+  OutputSurface(
+      std::unique_ptr<ContextProvider::Factory> compositor_context_factory,
+      scoped_refptr<ContextProvider> worker_context_provider);
+  explicit OutputSurface(
+      std::unique_ptr<ContextProvider::Factory> compositor_context_factory);
   explicit OutputSurface(std::unique_ptr<SoftwareOutputDevice> software_device);
 
-  OutputSurface(scoped_refptr<ContextProvider> context_provider,
-                std::unique_ptr<SoftwareOutputDevice> software_device);
+  OutputSurface(
+      std::unique_ptr<ContextProvider::Factory> compositor_context_factory,
+      std::unique_ptr<SoftwareOutputDevice> software_device);
 
   ~OutputSurface() override;
 
@@ -98,7 +102,9 @@ class CC_EXPORT OutputSurface : public base::trace_event::MemoryDumpProvider {
   // surface. Either of these may return a null pointer, but not both.
   // In the event of a lost context, the entire output surface should be
   // recreated.
-  ContextProvider* context_provider() const { return context_provider_.get(); }
+  ContextProvider* context_provider() const {
+    return compositor_context_provider_.get();
+  }
   ContextProvider* worker_context_provider() const {
     return worker_context_provider_.get();
   }
@@ -177,7 +183,8 @@ class CC_EXPORT OutputSurface : public base::trace_event::MemoryDumpProvider {
   void PostSwapBuffersComplete();
 
   struct OutputSurface::Capabilities capabilities_;
-  scoped_refptr<ContextProvider> context_provider_;
+  std::unique_ptr<ContextProvider::Factory> compositor_context_factory_;
+  scoped_refptr<ContextProvider> compositor_context_provider_;
   scoped_refptr<ContextProvider> worker_context_provider_;
   scoped_refptr<VulkanContextProvider> vulkan_context_provider_;
   std::unique_ptr<SoftwareOutputDevice> software_device_;