Perform navigation policy check on UI thread for --site-per-process.

content/browser/frame_host/interstitial_page_navigator_impl.h

Index: content/browser/frame_host/interstitial_page_navigator_impl.h
diff --git a/content/browser/frame_host/interstitial_page_navigator_impl.h b/content/browser/frame_host/interstitial_page_navigator_impl.h
index 2b57f7a899c416b08b1f7b957bb478822ca1cac5..707754661e0386b788727aa86a8b16d86b2b39fa 100644
--- a/content/browser/frame_host/interstitial_page_navigator_impl.h
+++ b/content/browser/frame_host/interstitial_page_navigator_impl.h
@@ -22,6 +22,7 @@ class CONTENT_EXPORT InterstitialPageNavigatorImpl : public Navigator {
       InterstitialPageImpl* interstitial,
       NavigationControllerImpl* navigation_controller);
 
+  virtual NavigationController* GetController() OVERRIDE;
   virtual void DidNavigate(
       RenderFrameHostImpl* render_frame_host,
       const FrameHostMsg_DidCommitProvisionalLoad_Params&
@@ -34,6 +35,9 @@ class CONTENT_EXPORT InterstitialPageNavigatorImpl : public Navigator {
   // Non owned pointer.
   InterstitialPageImpl* interstitial_;
 
+  // The NavigationController associated with this navigator.
+  NavigationControllerImpl* controller_;
+
   DISALLOW_COPY_AND_ASSIGN(InterstitialPageNavigatorImpl);
 };