Never connect a port to the same frame

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

 // 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.
 
 #include "chrome/browser/extensions/api/messaging/extension_message_port.h"
 
 #include "base/scoped_observer.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/render_frame_host.h"
@@ skipping 96 matching lines @@
   if (include_child_frames) {
     tab->ForEachFrame(base::Bind(&ExtensionMessagePort::RegisterFrame,
                                  base::Unretained(this)));
   } else {
     RegisterFrame(rfh);
   }
 }
 
 ExtensionMessagePort::~ExtensionMessagePort() {}
 
+void ExtensionMessagePort::RemoveCommonFrames(const MessagePort& port) {
+  // Avoid overlap in the set of frames to make sure that it does not matter
+  // when UnregisterFrame is called.
+  for (std::set<content::RenderFrameHost*>::iterator it = frames_.begin();
+       it != frames_.end(); ) {
+    if (port.HasFrame(*it)) {
+      frames_.erase(it++);
+    } else {
+      ++it;
+    }
+  }
+}
+
+bool ExtensionMessagePort::HasFrame(content::RenderFrameHost* rfh) const {
+  return frames_.find(rfh) != frames_.end();
+}
+
 bool ExtensionMessagePort::IsValidPort() {
   return !frames_.empty();
 }
 
 void ExtensionMessagePort::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,
@@ skipping 101 matching lines @@
     return;
   }
   for (content::RenderFrameHost* rfh : frames_) {
     IPC::Message* msg_copy = new IPC::Message(*msg.get());
     msg_copy->set_routing_id(rfh->GetRoutingID());
     rfh->Send(msg_copy);
   }
 }
 
 }  // namespace extensions