TemplateURLService: notify observers of shutdown

components/search_engines/template_url_service_observer.h

Index: components/search_engines/template_url_service_observer.h
diff --git a/components/search_engines/template_url_service_observer.h b/components/search_engines/template_url_service_observer.h
index acd016f583d77d3f20f36272cdf350ab0ccee61c..eb3ba6667d0b0dc243d75b1830cb3075e951e38d 100644
--- a/components/search_engines/template_url_service_observer.h
+++ b/components/search_engines/template_url_service_observer.h
@@ -12,6 +12,11 @@ class TemplateURLServiceObserver {
   // Notification that the template url model has changed in some way.
   virtual void OnTemplateURLServiceChanged() = 0;
 
+  // Notification that the template url service is shutting down. Observers that
+  // might outlive the service can use this to clear out any raw pointers to the
+  // service.
+  virtual void OnTemplateURLServiceShuttingDown() {}
+
  protected:
   virtual ~TemplateURLServiceObserver() {}
 };