Have ExtensionHost use TabContents instead of RenderViewHost. Try #2. The first

chrome/browser/extensions/extension_webnavigation_api.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.
 
 // Implements the Chrome Extensions WebNavigation API.
 
 #include "chrome/browser/extensions/extension_webnavigation_api.h"
 
 #include "base/json/json_writer.h"
 #include "base/lazy_instance.h"
@@ skipping 386 matching lines @@
   }
 }
 
 void ExtensionWebNavigationEventRouter::Retargeting(
     const content::RetargetingDetails* details) {
   if (details->source_frame_id == 0)
     return;
   ExtensionWebNavigationTabObserver* tab_observer =
       ExtensionWebNavigationTabObserver::Get(details->source_tab_contents);
   if (!tab_observer) {
-    NOTREACHED();
+    CHECK(details->source_tab_contents->GetRenderViewType() !=
+          content::VIEW_TYPE_TAB_CONTENTS);
     return;
   }
   const FrameNavigationState& frame_navigation_state =
       tab_observer->frame_navigation_state();
 
   if (!frame_navigation_state.CanSendEvents(details->source_frame_id))
     return;
 
   // If the TabContents was created as a response to an IPC from a renderer, it
   // doesn't yet have a wrapper, and we need to delay the extension event until
@@ skipping 305 matching lines @@
         keys::kFrameIdKey,
         GetFrameId(navigation_state.IsMainFrame(*frame), *frame));
     frameDict->SetBoolean(
         keys::kErrorOccurredKey,
         navigation_state.GetErrorOccurredInFrame(*frame));
     resultList->Append(frameDict);
   }
   result_.reset(resultList);
   return true;
 }