Deleted AppListViewDelegateObserver class (was unused).

chrome/browser/ui/app_list/app_list_view_delegate.h

Index: chrome/browser/ui/app_list/app_list_view_delegate.h
diff --git a/chrome/browser/ui/app_list/app_list_view_delegate.h b/chrome/browser/ui/app_list/app_list_view_delegate.h
index a1a27726afd009a76fe8133cfb22ef53210febaa..a65103019ea46dd15cded20f7f37b17780cf62f4 100644
--- a/chrome/browser/ui/app_list/app_list_view_delegate.h
+++ b/chrome/browser/ui/app_list/app_list_view_delegate.h
@@ -112,8 +112,6 @@ class AppListViewDelegate : public app_list::AppListViewDelegate,
 #endif
   bool IsSpeechRecognitionEnabled() override;
   const Users& GetUsers() const override;
-  void AddObserver(app_list::AppListViewDelegateObserver* observer) override;
-  void RemoveObserver(app_list::AppListViewDelegateObserver* observer) override;
 
   // Overridden from TemplateURLServiceObserver:
   void OnTemplateURLServiceChanged() override;
@@ -192,8 +190,6 @@ class AppListViewDelegate : public app_list::AppListViewDelegate,
   std::unique_ptr<AppSyncUIStateWatcher> app_sync_ui_state_watcher_;
 #endif
 
-  base::ObserverList<app_list::AppListViewDelegateObserver> observers_;
-
   ScopedObserver<TemplateURLService, AppListViewDelegate>
       template_url_service_observer_;