Don't call renderView methods in threaded mode

content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc

Index: content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc
diff --git a/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc b/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc
index 6f2b3254df126073298e9ffcb4857f862f257a00..ac6ad870288fdb5e529709c6deb7b0953267b68e 100644
--- a/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc
+++ b/content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc
@@ -23,6 +23,7 @@
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/synchronization/lock.h"
+#include "content/common/child_process.h"
 #include "content/public/common/content_switches.h"
 #include "content/renderer/gpu/command_buffer_proxy.h"
 #include "content/renderer/gpu/gpu_channel_host.h"
@@ -147,6 +148,14 @@ bool WebGraphicsContext3DCommandBufferImpl::MaybeInitializeGL() {
 
   TRACE_EVENT0("gpu", "WebGfxCtx3DCmdBfrImpl::MaybeInitializeGL");
 
+  // If the context is being initialized on something other than the main
+  // thread, then drop the web_view_ pointer so we don't accidentally
+  // dereference it.
+  MessageLoop* main_message_loop =
+      ChildProcess::current()->main_thread()->message_loop();
+  if (MessageLoop::current() != main_message_loop)
+    web_view_ = NULL;
+
   // Convert WebGL context creation attributes into RendererGLContext / EGL size
   // requests.
   const int alpha_size = attributes_.alpha ? 8 : 0;