Remove the --ui-enable-threaded-compositing flag.

ui/compositor/compositor.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 260 matching lines @@
 
   ContextFactory::GetInstance()->RemoveCompositor(this);
 }
 
 // static
 void Compositor::Initialize() {
 #if defined(OS_CHROMEOS)
   bool use_thread = !CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kUIDisableThreadedCompositing);
 #else
-  bool use_thread =
-      CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kUIEnableThreadedCompositing) &&
-      !CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kUIDisableThreadedCompositing);
+  bool use_thread = false;
 #endif
   if (use_thread) {
     g_compositor_thread = new base::Thread("Browser Compositor");
     g_compositor_thread->Start();
   }
 
   DCHECK(!g_compositor_initialized) << "Compositor initialized twice.";
   g_compositor_initialized = true;
 }
 
@@ skipping 263 matching lines @@
     // CompositorObservers to be notified before starting another
     // draw cycle.
     ScheduleDraw();
   }
   FOR_EACH_OBSERVER(CompositorObserver,
                     observer_list_,
                     OnCompositingEnded(this));
 }
 
 }  // namespace ui