Refactor GuestViewContainer to split out WebView related logic and MimeHandlerView related logic.

extensions/common/extension_messages.h

 // 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.
 
 // IPC messages for extensions.
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 #include <vector>
 
@@ skipping 500 matching lines @@
 // an acknowledgement even if the RenderView has closed or navigated away.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_TransferBlobs,
                      std::vector<std::string> /* blob_uuids */)
 
 // The ACK for ExtensionHostMsg_CreateMimeHandlerViewGuest.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_CreateMimeHandlerViewGuestACK,
                      int /* element_instance_id */)
 
 // Once a RenderView proxy has been created for the guest in the embedder render
 // process, this IPC informs the embedder of the proxy's routing ID.
-IPC_MESSAGE_ROUTED2(ExtensionMsg_GuestAttached,
-                    int /* element_instance_id */,
+IPC_MESSAGE_ROUTED1(ExtensionMsg_GuestAttached,
                     int /* source_routing_id */)
 
 // Messages sent from the renderer to the browser.
 
 // A renderer sends this message when an extension process starts an API
 // request. The browser will always respond with a ExtensionMsg_Response.
 IPC_MESSAGE_ROUTED1(ExtensionHostMsg_Request,
                     ExtensionHostMsg_Request_Params)
 
 // A renderer sends this message when an extension process starts an API
@@ skipping 210 matching lines @@
                      int /* element_instance_id */,
                      int /* guest_instance_id */,
                      base::DictionaryValue /* attach_params */)
 
 // Tells the browser to create a mime handler guest view for a plugin.
 IPC_MESSAGE_CONTROL4(ExtensionHostMsg_CreateMimeHandlerViewGuest,
                      int /* render_frame_id */,
                      std::string /* embedder_url */,
                      std::string /* mime_type */,
                      int /* element_instance_id */)