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

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

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_SETTINGS_PRIVATE_EVENT_ROUTER_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_SETTINGS_PRIVATE_EVENT_ROUTER_H_
 
 #include <memory>
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "chrome/browser/chromeos/settings/cros_settings.h"
 #include "chrome/browser/extensions/api/settings_private/prefs_util.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "extensions/browser/event_router.h"
 
 namespace content {
 class BrowserContext;
 }
 
@@ skipping 27 matching lines @@
 
  private:
   // Decide if we should listen for pref changes or not. If there are any
   // JavaScript listeners registered for the onPrefsChanged event, then we
   // want to register for change notification from the PrefChangeRegistrar.
   // Otherwise, we want to unregister and not be listening for pref changes.
   void StartOrStopListeningForPrefsChanges();
 
   void OnPreferenceChanged(const std::string& pref_name);
 
+  // Sends a pref change to any listeners (if they exist; no-ops otherwise).
+  void SendPrefChange(const std::string& pref_name);
+
   PrefChangeRegistrar* FindRegistrarForPref(const std::string& pref_name);
 
   using SubscriptionMap =
       std::map<std::string,
                std::unique_ptr<chromeos::CrosSettings::ObserverSubscription>>;
   SubscriptionMap cros_settings_subscription_map_;
 
   content::BrowserContext* context_;
   bool listening_;
 
   std::unique_ptr<PrefsUtil> prefs_util_;
 
+  base::WeakPtrFactory<SettingsPrivateEventRouter> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(SettingsPrivateEventRouter);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_SETTINGS_PRIVATE_EVENT_ROUTER_H_