Create a new RenderFrameHost per child frame when --site-per-process is enabled.

ipc/ipc_message_start.h

 // Copyright 2012 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.
 
 #ifndef IPC_IPC_MESSAGE_START_H_
 #define IPC_IPC_MESSAGE_START_H_
 
 // Used by IPC_BEGIN_MESSAGES so that each message class starts from a unique
 // base.  Messages have unique IDs across channels in order for the IPC logging
 // code to figure out the message class from its ID.
 enum IPCMessageStart {
   AutomationMsgStart = 0,
+  FrameMsgStart,
   ViewMsgStart,
   InputMsgStart,
   PluginMsgStart,
   PluginProcessMsgStart,
   ProfileImportMsgStart,
   TestMsgStart,
   DevToolsMsgStart,
   WorkerMsgStart,
   NaClMsgStart,
   UtilityMsgStart,
@@ skipping 62 matching lines @@
   MemoryBenchmarkMsgStart,
   WebSocketMsgStart,
   NaClHostMsgStart,
   WebRTCIdentityMsgStart,
   LocalDiscoveryMsgStart,
   PowerMonitorMsgStart,
   LastIPCMsgStart      // Must come last.
 };
 
 #endif  // IPC_IPC_MESSAGE_START_H_