Make GetDisplayedNotifications asynchronous.

chrome/browser/notifications/platform_notification_service_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/notifications/platform_notification_service_impl.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/metrics/histogram_macros.h"
@@ skipping 361 matching lines @@
 
   Profile* profile = Profile::FromBrowserContext(browser_context);
   DCHECK(profile);
 
   closed_notifications_.insert(notification_id);
 
   GetNotificationDisplayService(profile)->Close(NotificationCommon::PERSISTENT,
                                                 notification_id);
 }
 
-bool PlatformNotificationServiceImpl::GetDisplayedNotifications(
+void PlatformNotificationServiceImpl::GetDisplayedNotifications(
     BrowserContext* browser_context,
-    std::set<std::string>* displayed_notifications) {
-  DCHECK(displayed_notifications);
+    const NotificationResultCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   Profile* profile = Profile::FromBrowserContext(browser_context);
-  if (!profile || profile->AsTestingProfile())
-    return false;  // Tests will not have a message center.
-
-  return GetNotificationDisplayService(profile)->GetDisplayed(
-      displayed_notifications);
+  // Tests will not have a message center.
+  if (!profile || profile->AsTestingProfile()) {
+    std::unique_ptr<std::set<std::string>> displayedNotifications =

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

displayed_notifications or delete per the comment on the
PlatformNotificationService interface

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

Done.

+        base::MakeUnique<std::set<std::string>>();
+    content::BrowserThread::PostTask(
+        content::BrowserThread::UI, FROM_HERE,
+        base::Bind(callback, base::Passed(&displayedNotifications),
+                   false /* supports getting displayed notifications */));

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

I'd just take the easy path here and use:

  callback.Run(std::move(displayed_notifications), false /* supported */);

You are on the UI thread, and there's only a single user of the //content API.

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

Done.

+    return;
+  }
+  GetNotificationDisplayService(profile)->GetDisplayed(callback);
 }
 
 void PlatformNotificationServiceImpl::OnClickEventDispatchComplete(
     content::PersistentNotificationStatus status) {
   UMA_HISTOGRAM_ENUMERATION(
       "Notifications.PersistentWebNotificationClickResult", status,
       content::PersistentNotificationStatus::
           PERSISTENT_NOTIFICATION_STATUS_MAX);
 #if BUILDFLAG(ENABLE_BACKGROUND)
   DCHECK_GT(pending_click_dispatch_events_, 0);
@@ skipping 118 matching lines @@
   }
 #endif
 
   return base::string16();
 }
 
 void PlatformNotificationServiceImpl::SetNotificationDisplayServiceForTesting(
     NotificationDisplayService* display_service) {
   test_display_service_ = display_service;
 }