Use WebCompositor only when --enable-threaded-compositing.

content/renderer/render_thread_impl.cc

 // Copyright (c) 2011 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 "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <vector>
@@ skipping 413 matching lines @@
   if (webkit_platform_support_.get())
     return;
 
   v8::V8::SetCounterFunction(base::StatsTable::FindLocation);
   v8::V8::SetCreateHistogramFunction(CreateHistogram);
   v8::V8::SetAddHistogramSampleFunction(AddHistogramSample);
 
   webkit_platform_support_.reset(new RendererWebKitPlatformSupportImpl);
   WebKit::initialize(webkit_platform_support_.get());
 
-  compositor_thread_.reset(new CompositorThread(this));
-  AddFilter(compositor_thread_->GetMessageFilter());
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableThreadedCompositing)) {
+    compositor_thread_.reset(new CompositorThread(this));
+    AddFilter(compositor_thread_->GetMessageFilter());
+  }
 
   WebScriptController::enableV8SingleThreadMode();
 
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
 
   webkit_glue::EnableWebCoreLogChannels(
       command_line.GetSwitchValueASCII(switches::kWebCoreLogChannels));
 
   if (command_line.HasSwitch(switches::kPlaybackMode) ||
       command_line.HasSwitch(switches::kRecordMode) ||
@@ skipping 326 matching lines @@
 
 scoped_refptr<base::MessageLoopProxy>
 RenderThreadImpl::GetFileThreadMessageLoopProxy() {
   DCHECK(message_loop() == MessageLoop::current());
   if (!file_thread_.get()) {
     file_thread_.reset(new base::Thread("Renderer::FILE"));
     file_thread_->Start();
   }
   return file_thread_->message_loop_proxy();
 }