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

chrome/browser/extensions/extension_webnavigation_api.cc

Index: chrome/browser/extensions/extension_webnavigation_api.cc
diff --git a/chrome/browser/extensions/extension_webnavigation_api.cc b/chrome/browser/extensions/extension_webnavigation_api.cc
index 0cc2d0195947d6d31db46c3c7d96ebdfaa3601ad..5e54ef244834839f0871c42e3c69392d0fb55be5 100644
--- a/chrome/browser/extensions/extension_webnavigation_api.cc
+++ b/chrome/browser/extensions/extension_webnavigation_api.cc
@@ -404,7 +404,8 @@ void ExtensionWebNavigationEventRouter::Retargeting(
   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 =