Plumb Blink notification actions to button UI on desktop

content/child/notifications/notification_manager.cc

Index: content/child/notifications/notification_manager.cc
diff --git a/content/child/notifications/notification_manager.cc b/content/child/notifications/notification_manager.cc
index 70a61403338484657403e5b8292d2919f8fbed93..95195455295633da3dab73e4b12351c0e8c3303e 100644
--- a/content/child/notifications/notification_manager.cc
+++ b/content/child/notifications/notification_manager.cc
@@ -16,6 +16,7 @@
 #include "content/child/service_worker/web_service_worker_registration_impl.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/child/worker_task_runner.h"
+#include "content/common/notification_constants.h"
 #include "content/public/common/platform_notification_data.h"
 #include "third_party/WebKit/public/platform/WebSecurityOrigin.h"
 #include "third_party/WebKit/public/platform/modules/notifications/WebNotificationDelegate.h"
@@ -220,6 +221,10 @@ WebNotificationPermission NotificationManager::checkPermission(
   return permission;
 }
 
+size_t NotificationManager::maxActions() {
+  return kPlatformNotificationMaxActions;
+}
+
 bool NotificationManager::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(NotificationManager, message)