Don't call renderView methods in threaded mode

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 15320c1d5be0d8e75faf377d5bd1496620fc2617..d3f498babac262348fed5a89a70530db9d878929 100644
--- a/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h
+++ b/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h
@@ -494,7 +494,9 @@ class WebGraphicsContext3DCommandBufferImpl
   int32 render_view_routing_id_;
 
   bool render_directly_to_web_view_;
+
   // If rendering directly to WebView, weak pointer to it.
+  // This is only set when the context is bound to the main thread.
   WebKit::WebView* web_view_;
 
 #if defined(OS_MACOSX)