Make GetDisplayedNotifications asynchronous.

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..76bb5a0e12eb40ede3eab042dda4c78aa4649afe 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,
@@ -32,12 +33,16 @@ void MessageCenterDisplayService::Close(
                           NotificationUIManager::GetProfileID(profile_));
 }
 
-bool MessageCenterDisplayService::GetDisplayed(
-    std::set<std::string>* notifications) const {
-  DCHECK(notifications);
+void MessageCenterDisplayService::GetDisplayed(
+    const NotificationResultCallback& callback) const {
+  std::unique_ptr<std::set<std::string>> displayed_notifications =
+      base::MakeUnique<std::set<std::string>>();

[Peter Beverloo, 2017/03/15 18:07:50]

note: I think `auto` is a reasonable thing for this sort of declaration

  auto notifications = base::MakeUnique<std::set<std::string>>();

[Miguel Garcia, 2017/03/16 14:57:42]

Done.

   for (auto notification_id : ui_manager_->GetAllIdsByProfile(
            NotificationUIManager::GetProfileID(profile_))) {
-    notifications->insert(notification_id);
+    displayed_notifications->insert(notification_id);
   }
-  return true;
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI, FROM_HERE,
+      base::Bind(callback, base::Passed(&displayed_notifications),
+                 true /* supports sync */));
 }