Prevent Pepper plugin reentrncy for synchronous messages.

ppapi/proxy/ppb_instance_proxy.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 "ppapi/proxy/ppb_instance_proxy.h"
 
 #include "ppapi/c/pp_var.h"
 #include "ppapi/c/ppb_instance.h"
+#include "ppapi/proxy/host_dispatcher.h"
 #include "ppapi/proxy/plugin_dispatcher.h"
 #include "ppapi/proxy/plugin_resource.h"
 #include "ppapi/proxy/plugin_resource_tracker.h"
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/serialized_var.h"
 
 namespace pp {
 namespace proxy {
 
 namespace {
@@ skipping 141 matching lines @@
 void PPB_Instance_Proxy::OnMsgIsFullFrame(PP_Instance instance,
                                           PP_Bool* result) {
   *result = ppb_instance_target()->IsFullFrame(instance);
 }
 
 void PPB_Instance_Proxy::OnMsgExecuteScript(
     PP_Instance instance,
     SerializedVarReceiveInput script,
     SerializedVarOutParam out_exception,
     SerializedVarReturnValue result) {
+  if (dispatcher()->IsPlugin())
+    NOTREACHED();
+  else
+    static_cast<HostDispatcher*>(dispatcher())->set_allow_plugin_reentrancy();
+
   result.Return(dispatcher(), ppb_instance_target()->ExecuteScript(
       instance,
       script.Get(dispatcher()),
       out_exception.OutParam(dispatcher())));
 }
 
 }  // namespace proxy
 }  // namespace pp