Reduce FOR_EACH_OBSERVER usage in extensions

extensions/browser/app_window/app_window_registry.cc

Index: extensions/browser/app_window/app_window_registry.cc
diff --git a/extensions/browser/app_window/app_window_registry.cc b/extensions/browser/app_window/app_window_registry.cc
index 6fc0dedccfabd7cb140f09bdbd72a3a79e94435e..c02424291bf7c52fc8c6c4668859b488e2a3e171 100644
--- a/extensions/browser/app_window/app_window_registry.cc
+++ b/extensions/browser/app_window/app_window_registry.cc
@@ -62,26 +62,30 @@ AppWindowRegistry* AppWindowRegistry::Get(content::BrowserContext* context) {
 
 void AppWindowRegistry::AddAppWindow(AppWindow* app_window) {
   BringToFront(app_window);
-  FOR_EACH_OBSERVER(Observer, observers_, OnAppWindowAdded(app_window));
+  for (auto& observer : observers_)
+    observer.OnAppWindowAdded(app_window);
 }
 
 void AppWindowRegistry::AppWindowIconChanged(AppWindow* app_window) {
   AddAppWindowToList(app_window);
-  FOR_EACH_OBSERVER(Observer, observers_, OnAppWindowIconChanged(app_window));
+  for (auto& observer : observers_)
+    observer.OnAppWindowIconChanged(app_window);
 }
 
 void AppWindowRegistry::AppWindowActivated(AppWindow* app_window) {
   BringToFront(app_window);
-  FOR_EACH_OBSERVER(Observer, observers_, OnAppWindowActivated(app_window));
+  for (auto& observer : observers_)
+    observer.OnAppWindowActivated(app_window);
 }
 
 void AppWindowRegistry::AppWindowHidden(AppWindow* app_window) {
-  FOR_EACH_OBSERVER(Observer, observers_, OnAppWindowHidden(app_window));
+  for (auto& observer : observers_)
+    observer.OnAppWindowHidden(app_window);
 }
 
 void AppWindowRegistry::AppWindowShown(AppWindow* app_window, bool was_hidden) {
-  FOR_EACH_OBSERVER(Observer, observers_,
-                    OnAppWindowShown(app_window, was_hidden));
+  for (auto& observer : observers_)
+    observer.OnAppWindowShown(app_window, was_hidden);
 }
 
 void AppWindowRegistry::RemoveAppWindow(AppWindow* app_window) {
@@ -89,7 +93,8 @@ void AppWindowRegistry::RemoveAppWindow(AppWindow* app_window) {
       std::find(app_windows_.begin(), app_windows_.end(), app_window);
   if (it != app_windows_.end())
     app_windows_.erase(it);
-  FOR_EACH_OBSERVER(Observer, observers_, OnAppWindowRemoved(app_window));
+  for (auto& observer : observers_)
+    observer.OnAppWindowRemoved(app_window);
 }
 
 void AppWindowRegistry::AddObserver(Observer* observer) {