Never connect a port to the same frame

chrome/browser/extensions/api/messaging/extension_message_port.h

 // Copyright (c) 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 CHROME_BROWSER_EXTENSIONS_API_MESSAGING_EXTENSION_MESSAGE_PORT_H_
 #define CHROME_BROWSER_EXTENSIONS_API_MESSAGING_EXTENSION_MESSAGE_PORT_H_
 
 #include "base/macros.h"
 #include "chrome/browser/extensions/api/messaging/message_service.h"
 
@@ skipping 23 matching lines @@
                        content::RenderFrameHost* rfh,
                        bool include_child_frames);
   // Create a port that is tied to all frames of an extension, possibly spanning
   // multiple tabs, including the invisible background page, popups, etc.
   ExtensionMessagePort(base::WeakPtr<MessageService> message_service,
                        int port_id,
                        const std::string& extension_id,
                        content::RenderProcessHost* extension_process);
   ~ExtensionMessagePort() override;
 
+  // MessageService::MessagePort:
+  void RemoveCommonFrames(const MessagePort& port) override;
+  bool HasFrame(content::RenderFrameHost* rfh) const override;
   bool IsValidPort() override;
-
-  // MessageService::MessagePort:
   void DispatchOnConnect(const std::string& channel_name,
                          scoped_ptr<base::DictionaryValue> source_tab,
                          int source_frame_id,
                          int guest_process_id,
                          int guest_render_frame_routing_id,
                          const std::string& source_extension_id,
                          const std::string& target_extension_id,
                          const GURL& source_url,
                          const std::string& tls_channel_id) override;
   void DispatchOnDisconnect(const std::string& error_message) override;
@@ skipping 41 matching lines @@
 
   ExtensionHost* background_host_ptr_;  // used in IncrementLazyKeepaliveCount
   scoped_ptr<FrameTracker> frame_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionMessagePort);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_MESSAGING_EXTENSION_MESSAGE_PORT_H_