Fix some issues with extension messaging:

chrome/browser/extensions/extension_host.cc

 // Copyright (c) 2006-2009 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_host.h"
 
 #include "app/l10n_util.h"
 #include "app/resource_bundle.h"
 #include "base/string_util.h"
 #include "chrome/browser/browser.h"
@@ skipping 131 matching lines @@
 void ExtensionHost::UpdatePreferredWidth(int pref_width) {
 #if defined(OS_WIN)
   if (view_.get())
     view_->DidContentsPreferredWidthChange(pref_width);
 #endif
 }
 
 void ExtensionHost::RenderViewGone(RenderViewHost* render_view_host) {
   DCHECK_EQ(render_view_host_, render_view_host);
   TabContents* current_tab = GetBrowser()->GetSelectedTabContents();
-  DCHECK(current_tab);
   if (current_tab) {
     current_tab->AddInfoBar(
         new CrashedExtensionInfobarDelegate(current_tab, this));
   }
   NotificationService::current()->Notify(
       NotificationType::EXTENSION_PROCESS_CRASHED,
       Source<Profile>(profile_),
       Details<ExtensionHost>(this));
 }
 
@@ skipping 141 matching lines @@
                                         int request_id,
                                         bool has_callback) {
   extension_function_dispatcher_->HandleRequest(message, content, request_id,
                                                 has_callback);
 }
 
 void ExtensionHost::RenderViewCreated(RenderViewHost* render_view_host) {
   extension_function_dispatcher_.reset(
       new ExtensionFunctionDispatcher(render_view_host_, this, url_));
 }