[MacViews] Implement ChromeNativeAppWindowViewsMac::FlashFrame.

chrome/browser/ui/views/apps/chrome_native_app_window_views_mac.mm

Index: chrome/browser/ui/views/apps/chrome_native_app_window_views_mac.mm
diff --git a/chrome/browser/ui/views/apps/chrome_native_app_window_views_mac.mm b/chrome/browser/ui/views/apps/chrome_native_app_window_views_mac.mm
index 3356dcbb7fce26c814515eef47ba558206a9f737..1d2f0fdb5e8dd02c479f30bfddd408345cdbe2b0 100644
--- a/chrome/browser/ui/views/apps/chrome_native_app_window_views_mac.mm
+++ b/chrome/browser/ui/views/apps/chrome_native_app_window_views_mac.mm
@@ -50,6 +50,12 @@ void ChromeNativeAppWindowViewsMac::ShowInactive() {
   ChromeNativeAppWindowViews::ShowInactive();
 }
 
+void ChromeNativeAppWindowViewsMac::FlashFrame(bool flash) {
+  apps::ExtensionAppShimHandler::RequestUserAttentionForWindow(
+      app_window(), flash ? apps::APP_SHIM_ATTENTION_CRITICAL
+                          : apps::APP_SHIM_ATTENTION_CANCEL);
+}
+
 void ChromeNativeAppWindowViewsMac::ShowWithApp() {
   is_hidden_with_app_ = false;
   if (!app_window()->is_hidden())