Make GetDisplayedNotifications asynchronous.

content/browser/notifications/platform_notification_context_impl.cc

Index: content/browser/notifications/platform_notification_context_impl.cc
diff --git a/content/browser/notifications/platform_notification_context_impl.cc b/content/browser/notifications/platform_notification_context_impl.cc
index 2cf1d983d52598f7617eb996171e03f02a47b8b0..7ea67aef86d52aadeefc0ea5ae98bc1872bfeb5e 100644
--- a/content/browser/notifications/platform_notification_context_impl.cc
+++ b/content/browser/notifications/platform_notification_context_impl.cc
@@ -57,36 +57,51 @@ void PlatformNotificationContextImpl::Initialize() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   PlatformNotificationService* service =
       GetContentClient()->browser()->GetPlatformNotificationService();
-  if (service) {
-    std::set<std::string> displayed_notifications;
-
-    bool notification_synchronization_supported =
-        service->GetDisplayedNotifications(browser_context_,
-                                           &displayed_notifications);
-
-    // Synchronize the notifications stored in the database with the set of
-    // displaying notifications in |displayed_notifications|. This is necessary
-    // because flakiness may cause a platform to inform Chrome of a notification
-    // that has since been closed, or because the platform does not support
-    // notifications that exceed the lifetime of the browser process.
-
-    // TODO(peter): Synchronizing the actual notifications will be done when the
-    // persistent notification ids are stable. For M44 we need to support the
-    // case where there may be no notifications after a Chrome restart.
-    if (notification_synchronization_supported &&
-        displayed_notifications.empty()) {
-      prune_database_on_open_ = true;
-    }
+  if (!service) {

[Peter Beverloo, 2017/03/15 18:07:51]

Here's an idea: should we maybe just bail out if there's no service? It's not
like there'll be data in the database in that scenario, or that registering a
Service Worker observer is going to be helpful...

  // There is no need to initialize the platform notification context if the
  // embedder-provided service is not available.
  if (!GetContentClient()->browser()->GetPlatformNotificationService())
    return;

That saves you quite some code here, as well as having the {Initialize,
InitializeOnUI, InitializeOnIO} triple.

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

Done.

[Miguel Garcia, 2017/03/16 15:57:25]

I had to revert this because several tests fail as they expect to eventually be
called with the available notifications.

+    std::unique_ptr<std::set<std::string>> displayed_notifications =
+        base::MakeUnique<std::set<std::string>>();
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(&PlatformNotificationContextImpl::InitializeOnIO, this,
+                   base::Passed(&displayed_notifications), false));
+    return;
   }
+  service->GetDisplayedNotifications(
+      browser_context_,
+      base::Bind(&PlatformNotificationContextImpl::InitializeOnUI, this));
+}
 
+void PlatformNotificationContextImpl::InitializeOnUI(
+    std::unique_ptr<std::set<std::string>> displayed_notifications,
+    bool notification_synchronization_supported) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
-      base::Bind(&PlatformNotificationContextImpl::InitializeOnIO, this));
+      base::Bind(&PlatformNotificationContextImpl::InitializeOnIO, this,
+                 base::Passed(&displayed_notifications),
+                 notification_synchronization_supported));
 }
 
-void PlatformNotificationContextImpl::InitializeOnIO() {
+void PlatformNotificationContextImpl::InitializeOnIO(
+    std::unique_ptr<std::set<std::string>> displayed_notifications,
+    bool notification_synchronization_supported) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
+  // Synchronize the notifications stored in the database with the set of
+  // displaying notifications in |displayed_notifications|. This is necessary
+  // because flakiness may cause a platform to inform Chrome of a notification
+  // that has since been closed, or because the platform does not support
+  // notifications that exceed the lifetime of the browser process.
+
+  // TODO(peter): Synchronizing the actual notifications will be done when the
+  // persistent notification ids are stable. For M44 we need to support the
+  // case where there may be no notifications after a Chrome restart.
+
+  if (notification_synchronization_supported &&
+      displayed_notifications->empty()) {
+    prune_database_on_open_ = true;
+  }
+
   // |service_worker_context_| may be NULL in tests.
   if (service_worker_context_)
     service_worker_context_->AddObserver(this);
@@ -181,7 +196,25 @@ void PlatformNotificationContextImpl::DoReadNotificationData(
 }
 
 void PlatformNotificationContextImpl::
-    SynchronizeDisplayedNotificationsForServiceWorkerRegistration(
+    SynchronizeDisplayedNotificationsForServiceWorkerRegistrationOnUI(
+        const GURL& origin,
+        int64_t service_worker_registration_id,
+        const ReadAllResultCallback& callback,
+        std::unique_ptr<std::set<std::string>> notification_ids,
+        bool sync_supported) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(
+          &PlatformNotificationContextImpl::
+              SynchronizeDisplayedNotificationsForServiceWorkerRegistrationOnIO,
+          this, origin, service_worker_registration_id, callback,
+          base::Passed(&notification_ids), sync_supported));
+}
+
+void PlatformNotificationContextImpl::
+    SynchronizeDisplayedNotificationsForServiceWorkerRegistrationOnIO(
         const GURL& origin,
         int64_t service_worker_registration_id,
         const ReadAllResultCallback& callback,
@@ -212,24 +245,21 @@ void PlatformNotificationContextImpl::
 
   if (!service) {
     // Rely on the database only
-    SynchronizeDisplayedNotificationsForServiceWorkerRegistration(
+    SynchronizeDisplayedNotificationsForServiceWorkerRegistrationOnIO(
         origin, service_worker_registration_id, callback,
         std::move(notification_ids), false /* sync_supported */);

[Peter Beverloo, 2017/03/15 18:07:51]

Here too, maybe we should just drop out?

    callback.Run(false /* success */, std::vector<NotificationDatabaseData>());

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

I think we have some tests that rely on this right?

     return;
   }
 
-  std::set<std::string>* notification_ids_ptr = notification_ids.get();
-
-  BrowserThread::PostTaskAndReplyWithResult(
+  BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
-      base::Bind(&PlatformNotificationService::GetDisplayedNotifications,
-                 base::Unretained(service), browser_context_,
-                 notification_ids_ptr),
       base::Bind(
-          &PlatformNotificationContextImpl::
-              SynchronizeDisplayedNotificationsForServiceWorkerRegistration,
-          this, origin, service_worker_registration_id, callback,
-          base::Passed(&notification_ids)));
+          &PlatformNotificationService::GetDisplayedNotifications,
+          base::Unretained(service), browser_context_,
+          base::Bind(
+              &PlatformNotificationContextImpl::
+                  SynchronizeDisplayedNotificationsForServiceWorkerRegistrationOnUI,
+              this, origin, service_worker_registration_id, callback)));
 }
 
 void PlatformNotificationContextImpl::