Attempt at a fix for ExtensionBrowserTest.MessagingContentScript.

chrome/browser/extensions/extension_message_service.cc

 // Copyright (c) 2009 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/extension_message_service.h"
 
 #include "base/json_writer.h"
 #include "base/singleton.h"
 #include "base/stl_util-inl.h"
 #include "base/values.h"
@@ skipping 135 matching lines @@
     extension_devtools_manager_->AddEventListener(event_name,
                                                   render_process_id);
   }
 }
 
 void ExtensionMessageService::RemoveEventListener(const std::string& event_name,
                                                   int render_process_id) {
   // It is possible that this RenderProcessHost is being destroyed.  If that is
   // the case, we'll have already removed his listeners, so do nothing here.
   RenderProcessHost* rph = RenderProcessHost::FromID(render_process_id);
-  if (!rph)
+  if (!rph || rph->ListenersIterator().IsAtEnd())
     return;
 
   DCHECK_EQ(MessageLoop::current()->type(), MessageLoop::TYPE_UI);
-  DCHECK_EQ(listeners_[event_name].count(render_process_id), 1u) << event_name;
+  DCHECK_EQ(listeners_[event_name].count(render_process_id), 1u)
+      << " PID=" << render_process_id << " event=" << event_name;
   listeners_[event_name].erase(render_process_id);
 
   if (extension_devtools_manager_.get()) {
     extension_devtools_manager_->RemoveEventListener(event_name,
                                                      render_process_id);
   }
 }
 
 void ExtensionMessageService::AllocatePortIdPair(int* port1, int* port2) {
   AutoLock lock(next_port_id_lock_);
@@ skipping 284 matching lines @@
   for (MessageChannelMap::iterator it = channels_.begin();
        it != channels_.end(); ) {
     MessageChannelMap::iterator current = it++;
     if (current->second->opener.sender == sender) {
       CloseChannelImpl(current, GET_CHANNEL_OPENER_ID(current->first));
     } else if (current->second->receiver.sender == sender) {
       CloseChannelImpl(current, GET_CHANNEL_RECEIVERS_ID(current->first));
     }
   }
 }