set cancel callback synchronously

fixes brave/browser-laptop#1931

brave/browser/notifications/platform_notification_service_impl.cc

@@ -20,6 +20,24 @@ namespace brave {
 
 namespace {
 
+class NotificationProxy : public base::SupportsWeakPtr<NotificationProxy> {
+ public:
+  explicit NotificationProxy() {}
+
+  void Dismiss() {
+    if (notification_)
+      notification_->Dismiss();
+  }
+
+  void set_notification(base::WeakPtr<brightray::Notification> notification) {
+    notification_ = notification;
+  }
+ private:
+  base::WeakPtr<brightray::Notification> notification_;
+
+  DISALLOW_COPY_AND_ASSIGN(NotificationProxy);
+};
+
 void OnPermissionResponse(const base::Callback<void(bool)>& callback,
                           blink::mojom::PermissionStatus status) {
   if (status == blink::mojom::PermissionStatus::GRANTED)
@@ -28,17 +46,16 @@ void OnPermissionResponse(const base::Callback<void(bool)>& callback,
     callback.Run(false);
 }
 
-void RemoveNotification(base::WeakPtr<brightray::Notification> notification) {
-  if (notification)
-    notification->Dismiss();
+void RemoveNotification(std::unique_ptr<NotificationProxy> notification_proxy) {
+  notification_proxy->Dismiss();
 }
 
 void OnWebNotificationAllowed(
     brightray::BrowserClient* browser_client,
     const SkBitmap& icon,
     const content::PlatformNotificationData& data,
     std::unique_ptr<content::DesktopNotificationDelegate> delegate,
-    base::Closure* cancel_callback,
+    const base::WeakPtr<NotificationProxy> notification_proxy,
     bool allowed) {
   if (!allowed)
     return;
@@ -51,8 +68,8 @@ void OnWebNotificationAllowed(
   if (notification) {
     ignore_result(adapter.release());  // it will release itself automatically.
     notification->Show(data.title, data.body, data.tag, data.icon, icon, data.silent);
-    if (cancel_callback)
-      *cancel_callback = base::Bind(&RemoveNotification, notification);
+    if (notification_proxy)
+      notification_proxy->set_notification(notification);
   }
 }
 
@@ -89,12 +106,22 @@ void PlatformNotificationServiceImpl::DisplayNotification(
     const content::NotificationResources& notification_resources,
     std::unique_ptr<content::DesktopNotificationDelegate> delegate,
     base::Closure* cancel_callback) {
+  // cancel_callback must be set when this method returns, but the
+  // RequestPermission callback may run asynchronously so we use
+  // the notification proxy as a placeholder until the actual
+  // notification is available
+  std::unique_ptr<NotificationProxy> notification_proxy(new NotificationProxy);
+
   auto callback = base::Bind(&OnWebNotificationAllowed,
              BraveContentBrowserClient::Get(),
              notification_resources.notification_icon,
              notification_data,
              base::Passed(&delegate),
-             cancel_callback);
+             notification_proxy->AsWeakPtr());
+
+  // TODO(bridiver) - there is a memory leak on mac because CocoaNotification never sends
+  // NotificationClosed to the PageNotificationDelegate
+  *cancel_callback = base::Bind(&RemoveNotification, base::Passed(&notification_proxy));
 
   auto permission_manager = browser_context->GetPermissionManager();
   permission_manager->RequestPermission(