Don't use GetAsTabContents. Send notifications from TabContentsView instead.

chrome/browser/tab_contents/background_contents.cc

Index: chrome/browser/tab_contents/background_contents.cc
diff --git a/chrome/browser/tab_contents/background_contents.cc b/chrome/browser/tab_contents/background_contents.cc
index b4eed25d610e1764d0737a42bf149614663a0d54..52a15dd519e15bf4c4bbc955d701f422c24c0773 100644
--- a/chrome/browser/tab_contents/background_contents.cc
+++ b/chrome/browser/tab_contents/background_contents.cc
@@ -209,16 +209,15 @@ void BackgroundContents::ProcessDOMUIMessage(
 
 void BackgroundContents::CreateNewWindow(
     int route_id,
-    WindowContainerType window_container_type,
-    const string16& frame_name) {
+    const ViewHostMsg_CreateWindow_Params& params) {
   delegate_view_helper_.CreateNewWindow(
       route_id,
       render_view_host_->process()->profile(),
       render_view_host_->site_instance(),
       DOMUIFactory::GetDOMUIType(render_view_host_->process()->profile(), url_),
       this,
-      window_container_type,
-      frame_name);
+      params.window_container_type,
+      params.frame_name);
 }
 
 void BackgroundContents::CreateNewWidget(int route_id,