Add command line switch for enabling threaded compositing

content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h

Index: content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h
diff --git a/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h b/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h
index 48e7d9a97dc0abed40736e526766935643285350..cece2907096951bcbd70643988dcc97e3aa7ac98 100644
--- a/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h
+++ b/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h
@@ -464,10 +464,9 @@ class WebGraphicsContext3DCommandBufferImpl
   int32 render_view_routing_id_;
 
   bool render_directly_to_web_view_;
-#ifndef WTF_USE_THREADED_COMPOSITING
   // If rendering directly to WebView, weak pointer to it.
   WebKit::WebView* web_view_;
-#endif
+
 #if defined(OS_MACOSX)
   // "Fake" plugin window handle in browser process for the compositor's output.
   gfx::PluginWindowHandle plugin_handle_;