Defer compositor context creation to the thread.

cc/test/pixel_test_output_surface.cc

Index: cc/test/pixel_test_output_surface.cc
diff --git a/cc/test/pixel_test_output_surface.cc b/cc/test/pixel_test_output_surface.cc
index 9250ee44cc1bb9b5c026fd13c80d79a1ba8bcee5..c0625c47b2b77b3591a05f46315abdeca92377b8 100644
--- a/cc/test/pixel_test_output_surface.cc
+++ b/cc/test/pixel_test_output_surface.cc
@@ -11,11 +11,12 @@
 namespace cc {
 
 PixelTestOutputSurface::PixelTestOutputSurface(
-    scoped_refptr<ContextProvider> context_provider,
+    std::unique_ptr<ContextProvider::Factory> compositor_context_factory,
     scoped_refptr<ContextProvider> worker_context_provider,
     bool flipped_output_surface,
     std::unique_ptr<BeginFrameSource> begin_frame_source)
-    : OutputSurface(context_provider, worker_context_provider),
+    : OutputSurface(std::move(compositor_context_factory),
+                    std::move(worker_context_provider)),
       begin_frame_source_(std::move(begin_frame_source)),
       external_stencil_test_(false) {
   capabilities_.adjust_deadline_for_parent = false;
@@ -23,15 +24,6 @@ PixelTestOutputSurface::PixelTestOutputSurface(
 }
 
 PixelTestOutputSurface::PixelTestOutputSurface(
-    scoped_refptr<ContextProvider> context_provider,
-    bool flipped_output_surface,
-    std::unique_ptr<BeginFrameSource> begin_frame_source)
-    : PixelTestOutputSurface(context_provider,
-                             nullptr,
-                             flipped_output_surface,
-                             std::move(begin_frame_source)) {}
-
-PixelTestOutputSurface::PixelTestOutputSurface(
     std::unique_ptr<SoftwareOutputDevice> software_device,
     std::unique_ptr<BeginFrameSource> begin_frame_source)
     : OutputSurface(std::move(software_device)),