MD Settings: defer sending pref updates until all synchronous operations finish

chrome/browser/extensions/api/settings_private/settings_private_event_router.cc

 // Copyright 2015 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/extensions/api/settings_private/settings_private_event_router.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/extensions/api/settings_private.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/browser_context.h"
 
 namespace extensions {
 
 SettingsPrivateEventRouter::SettingsPrivateEventRouter(
     content::BrowserContext* context)
-    : context_(context), listening_(false) {
+    : context_(context), listening_(false), weak_ptr_factory_(this) {
   // Register with the event router so we know when renderers are listening to
   // our events. We first check and see if there *is* an event router, because
   // some unit tests try to create all context services, but don't initialize
   // the event router first.
   EventRouter* event_router = EventRouter::Get(context_);
   if (event_router) {
     event_router->RegisterObserver(
         this, api::settings_private::OnPrefsChanged::kEventName);
     StartOrStopListeningForPrefsChanges();
   }
@@ skipping 82 matching lines @@
         cros_settings_subscription_map_.erase(it.first);
       else
         FindRegistrarForPref(it.first)->Remove(it.first);
     }
   }
   listening_ = should_listen;
 }
 
 void SettingsPrivateEventRouter::OnPreferenceChanged(
     const std::string& pref_name) {
+  // This posts an asynchronous task to ensure that all pref stores are updated,
+  // as |prefs_util_->GetPref()| relies on this information to determine if a
+  // preference is controlled by e.g. extensions.
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(&SettingsPrivateEventRouter::SendPrefChange,
+                            weak_ptr_factory_.GetWeakPtr(), pref_name));
+}
+
+void SettingsPrivateEventRouter::SendPrefChange(const std::string& pref_name) {
   EventRouter* event_router = EventRouter::Get(context_);
   if (!event_router->HasEventListener(
           api::settings_private::OnPrefsChanged::kEventName)) {
     return;
   }
 
   std::unique_ptr<api::settings_private::PrefObject> pref_object =
       prefs_util_->GetPref(pref_name);
 
   std::vector<api::settings_private::PrefObject> prefs;
   if (pref_object)
     prefs.push_back(std::move(*pref_object));
 
   std::unique_ptr<base::ListValue> args(
       api::settings_private::OnPrefsChanged::Create(prefs));
 
   std::unique_ptr<Event> extension_event(new Event(
       events::SETTINGS_PRIVATE_ON_PREFS_CHANGED,
       api::settings_private::OnPrefsChanged::kEventName, std::move(args)));
   event_router->BroadcastEvent(std::move(extension_event));
 }
 
 SettingsPrivateEventRouter* SettingsPrivateEventRouter::Create(
     content::BrowserContext* context) {
   return new SettingsPrivateEventRouter(context);
 }
 
 }  // namespace extensions