Prevent a possible crash on omnibox navigation.

chrome/browser/ui/omnibox/omnibox_navigation_observer.h

Index: chrome/browser/ui/omnibox/omnibox_navigation_observer.h
diff --git a/chrome/browser/ui/omnibox/omnibox_navigation_observer.h b/chrome/browser/ui/omnibox/omnibox_navigation_observer.h
index 82c9fd279837f98adc3666f1d0fff03cd5ae6111..e7f8717962446869ba53fb278ff49882edb9cafb 100644
--- a/chrome/browser/ui/omnibox/omnibox_navigation_observer.h
+++ b/chrome/browser/ui/omnibox/omnibox_navigation_observer.h
@@ -81,6 +81,10 @@ class OmniboxNavigationObserver : public content::NotificationObserver,
   void DidStartNavigationToPendingEntry(
       const GURL& url,
       content::NavigationController::ReloadType reload_type) override;
+  void DidFailProvisionalLoad(content::RenderFrameHost* render_frame_host,
+                              const GURL& validated_url,
+                              int error_code,
+                              const base::string16& error_description) override;
   void NavigationEntryCommitted(
       const content::LoadCommittedDetails& load_details) override;
   void WebContentsDestroyed() override;