Flip flag to turn CrOS Browser Compositor Single Threaded

Simply stop using threaded browser compositor for CrOS. Clean up would
be in follow up patch.

R=danakj@chromium.org, piman@chromium.org
BUG=329552

Review URL: https://codereview.chromium.org/781163003

Cr-Commit-Position: refs/heads/master@{#313842}

content/browser/compositor/gpu_process_transport_factory.cc

@@ -74,16 +74,7 @@ GpuProcessTransportFactory::GpuProcessTransportFactory()
       callback_factory_(this) {
   output_surface_proxy_ = new BrowserCompositorOutputSurfaceProxy(
       &output_surface_map_);
-#if defined(OS_CHROMEOS)
-  bool use_thread = !base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kUIDisableThreadedCompositing);
-#else
-  bool use_thread = false;
-#endif
-  if (use_thread) {
-    compositor_thread_.reset(new base::Thread("Browser Compositor"));
-    compositor_thread_->Start();
-  }
+
   if (UseSurfacesEnabled())
     surface_manager_ = make_scoped_ptr(new cc::SurfaceManager);
 }
@@ -247,7 +238,7 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
   if (!context_provider.get()) {
     if (compositor_thread_.get()) {
       LOG(FATAL) << "Failed to create UI context, but can't use software"
-                 " compositing with browser threaded compositing. Aborting.";
+                    " compositing with browser threaded compositing. Aborting.";
     }
 
     scoped_ptr<SoftwareBrowserCompositorOutputSurface> surface(

ui/compositor/test/in_process_context_factory.cc

@@ -69,17 +69,6 @@ InProcessContextFactory::InProcessContextFactory(bool context_factory_for_test)
   DCHECK_NE(gfx::GetGLImplementation(), gfx::kGLImplementationNone)
       << "If running tests, ensure that main() is calling "
       << "gfx::GLSurface::InitializeOneOffForTests()";
-
-#if defined(OS_CHROMEOS)
-  bool use_thread = !base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kUIDisableThreadedCompositing);
-#else
-  bool use_thread = false;
-#endif
-  if (use_thread) {
-    compositor_thread_.reset(new base::Thread("Browser Compositor"));
-    compositor_thread_->Start();
-  }
 }
 
 InProcessContextFactory::~InProcessContextFactory() {}