[Extensions] Fix thread-safety bug in PermissionsData

extensions/common/extension_messages.cc

 // Copyright 2014 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 "extensions/common/extension_messages.h"
 
 #include "content/public/common/common_param_traits.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest.h"
 #include "extensions/common/manifest_handler.h"
@@ skipping 42 matching lines @@
     bool include_tab_permissions)
     : manifest(extension->manifest()->value()->DeepCopy()),
       location(extension->location()),
       path(extension->path()),
       active_permissions(*extension->permissions_data()->active_permissions()),
       withheld_permissions(
           *extension->permissions_data()->withheld_permissions()),
       id(extension->id()),
       creation_flags(extension->creation_flags()) {
   if (include_tab_permissions) {
-    const extensions::PermissionsData::TabPermissionsMap& tab_permissions =
-        extension->permissions_data()->tab_specific_permissions();
+    extensions::PermissionsData::TabPermissionsMap tab_permissions =
+        extension->permissions_data()->CopyTabSpecificPermissionsMap();
     for (const auto& pair : tab_permissions) {
       tab_specific_permissions[pair.first] =
           ExtensionMsg_PermissionSetStruct(*pair.second);
     }
   }
 }
 
 scoped_refptr<Extension> ExtensionMsg_Loaded_Params::ConvertToExtension(
     std::string* error) const {
   scoped_refptr<Extension> extension =
@@ skipping 243 matching lines @@
          ReadParam(m, iter, &p->active_permissions) &&
          ReadParam(m, iter, &p->withheld_permissions);
 }
 
 void ParamTraits<ExtensionMsg_Loaded_Params>::Log(const param_type& p,
                                                   std::string* l) {
   l->append(p.id);
 }
 
 }  // namespace IPC