Deleted AppListViewDelegateObserver class (was unused).

ui/app_list/test/app_list_test_view_delegate.h

Index: ui/app_list/test/app_list_test_view_delegate.h
diff --git a/ui/app_list/test/app_list_test_view_delegate.h b/ui/app_list/test/app_list_test_view_delegate.h
index 0fc790231ac8670f650e1dd0439645dd4a28afef..21d7e85b04a37d1369456876779d33728ba39979 100644
--- a/ui/app_list/test/app_list_test_view_delegate.h
+++ b/ui/app_list/test/app_list_test_view_delegate.h
@@ -83,8 +83,6 @@ class AppListTestViewDelegate : public AppListViewDelegate {
 #endif
   bool IsSpeechRecognitionEnabled() override;
   const Users& GetUsers() const override;
-  void AddObserver(AppListViewDelegateObserver* observer) override;
-  void RemoveObserver(AppListViewDelegateObserver* observer) override;
 
   // Do a bulk replacement of the items in the model.
   void ReplaceTestModel(int item_count);
@@ -100,7 +98,6 @@ class AppListTestViewDelegate : public AppListViewDelegate {
   std::map<size_t, int> open_search_result_counts_;
   Users users_;
   std::unique_ptr<AppListTestModel> model_;
-  base::ObserverList<AppListViewDelegateObserver> observers_;
   SpeechUIModel speech_ui_;
   base::TimeDelta auto_launch_timeout_;