Retrive displayed notifications asynchronously

chrome/browser/notifications/message_center_display_service.cc

Index: chrome/browser/notifications/message_center_display_service.cc
diff --git a/chrome/browser/notifications/message_center_display_service.cc b/chrome/browser/notifications/message_center_display_service.cc
index 4ff6195539679db6630ccdf322ab00255048b322..aab92388e93f79f2c7e4c46a67043a281e8e0b2f 100644
--- a/chrome/browser/notifications/message_center_display_service.cc
+++ b/chrome/browser/notifications/message_center_display_service.cc
@@ -7,6 +7,7 @@
 #include "chrome/browser/notifications/notification.h"
 #include "chrome/browser/notifications/notification_ui_manager.h"
 #include "chrome/browser/profiles/profile.h"
+#include "content/public/browser/browser_thread.h"
 
 MessageCenterDisplayService::MessageCenterDisplayService(
     Profile* profile,
@@ -41,3 +42,14 @@ bool MessageCenterDisplayService::GetDisplayed(
   }
   return true;
 }
+
+void MessageCenterDisplayService::GetDisplayedAsync(
+    const NotificationCommon::NotificationResultCallback& callback) const {
+  std::unique_ptr<std::set<std::string>> displayed_notifications =
+      base::MakeUnique<std::set<std::string>>();
+  GetDisplayed(displayed_notifications.get());
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO, FROM_HERE,
+      base::Bind(callback, base::Passed(&displayed_notifications),
+                 true /* supports sync */));
+}