Revert of Flip flag to turn CrOS Browser Compositor Single Threaded (patchset...

Revert of Flip flag to turn CrOS Browser Compositor Single Threaded (patchset #5 id:80001 of https://codereview.chromium.org/781163003/)

Reason for revert:
Possible cause for veyron: Chrome crash in SW Mirror mode (at login screen)

https://code.google.com/p/chromium/issues/detail?id=453732

Original issue's description:
> 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
>
> Committed: https://crrev.com/e111a7d64d9ba12833900ab743beaf4ee6d267ed
> Cr-Commit-Position: refs/heads/master@{#313842}

TBR=danakj@chromium.org,piman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=329552

Review URL: https://codereview.chromium.org/893623002

Cr-Commit-Position: refs/heads/master@{#313950}

content/browser/compositor/gpu_process_transport_factory.cc

@@ -74,7 +74,16 @@ 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);
 }
@@ -238,7 +247,7 @@ 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

@@ -69,6 +69,17 @@ 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() {}