Add hook into pepper to query if running on the main thread.

webkit/glue/plugins/pepper_plugin_module.cc

 // Copyright (c) 2010 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 "webkit/glue/plugins/pepper_plugin_module.h"
 
 #include <set>
 
 #include "base/command_line.h"
 #include "base/message_loop.h"
@@ skipping 102 matching lines @@
 
 void CallOnMainThread(int delay_in_msec,
                       PP_CompletionCallback callback,
                       int32_t result) {
   GetMainThreadMessageLoop()->PostDelayedTask(
       FROM_HERE,
       NewRunnableFunction(callback.func, callback.user_data, result),
       delay_in_msec);
 }
 
+bool IsMainThread() {
+  return GetMainThreadMessageLoop()->BelongsToCurrentThread();
+}
+
 const PPB_Core core_interface = {
   &AddRefResource,
   &ReleaseResource,
   &MemAlloc,
   &MemFree,
   &GetTime,
-  &CallOnMainThread
+  &CallOnMainThread,
+  &IsMainThread
 };
 
 // PPB_Testing -----------------------------------------------------------------
 
 bool ReadImageData(PP_Resource device_context_2d,
                    PP_Resource image,
                    const PP_Point* top_left) {
   scoped_refptr<DeviceContext2D> context(
       Resource::GetAs<DeviceContext2D>(device_context_2d));
   if (!context.get())
@@ skipping 246 matching lines @@
 
 void PluginModule::InstanceCreated(PluginInstance* instance) {
   instances_.insert(instance);
 }
 
 void PluginModule::InstanceDeleted(PluginInstance* instance) {
   instances_.erase(instance);
 }
 
 }  // namespace pepper