Have ExtensionHost use TabContents instead of RenderViewHost. Try #3.

chrome/browser/extensions/extension_process_manager.cc

 // Copyright (c) 2011 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 "base/bind.h"
 #include "base/command_line.h"
 #include "chrome/browser/extensions/extension_process_manager.h"
 
 #include "chrome/browser/ui/browser_window.h"
 #include "content/browser/browsing_instance.h"
@@ skipping 182 matching lines @@
 
   ExtensionHost* host =
 #if defined(OS_MACOSX)
       new ExtensionHostMac(extension, GetSiteInstanceForURL(url), url,
                            chrome::VIEW_TYPE_EXTENSION_BACKGROUND_PAGE);
 #else
       new ExtensionHost(extension, GetSiteInstanceForURL(url), url,
                         chrome::VIEW_TYPE_EXTENSION_BACKGROUND_PAGE);
 #endif
 
-  host->CreateRenderViewSoon(NULL);  // create a RenderViewHost with no view
+  host->CreateRenderViewSoon();
   OnExtensionHostCreated(host, true);
 }
 
 void ExtensionProcessManager::OpenOptionsPage(const Extension* extension,
                                               Browser* browser) {
   DCHECK(!extension->options_url().is_empty());
 
   // Force the options page to open in non-OTR window, because it won't be
   // able to save settings from OTR.
   if (!browser || browser->profile()->IsOffTheRecord()) {
@@ skipping 276 matching lines @@
         if (service && service->is_ready())
           CreateBackgroundHostsForProfileStartup(this, service->extensions());
       }
       break;
     }
     default:
       ExtensionProcessManager::Observe(type, source, details);
       break;
   }
 }