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

chrome/browser/ui/views/extensions/extension_dialog.cc

Index: chrome/browser/ui/views/extensions/extension_dialog.cc
diff --git a/chrome/browser/ui/views/extensions/extension_dialog.cc b/chrome/browser/ui/views/extensions/extension_dialog.cc
index c2bc0b60e090f673eb0bba3f50be5093f3826a99..92e98ea0b8852ede8d542f7c2408e78c76adb3de 100644
--- a/chrome/browser/ui/views/extensions/extension_dialog.cc
+++ b/chrome/browser/ui/views/extensions/extension_dialog.cc
@@ -14,6 +14,7 @@
 #include "chrome/common/chrome_notification_types.h"
 #include "content/browser/renderer_host/render_view_host.h"
 #include "content/browser/renderer_host/render_widget_host_view.h"
+#include "content/browser/tab_contents/tab_contents.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"
 #include "googleurl/src/gurl.h"
@@ -73,7 +74,7 @@ ExtensionDialog* ExtensionDialog::Show(
   ExtensionDialog* dialog = new ExtensionDialog(host, observer);
   dialog->InitWindow(browser, width, height);
   // Ensure the DOM JavaScript can respond immediately to keyboard shortcuts.
-  host->render_view_host()->view()->Focus();
+  host->host_contents()->Focus();
   return dialog;
 }