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

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

Index: chrome/browser/extensions/api/settings_private/settings_private_event_router.h
diff --git a/chrome/browser/extensions/api/settings_private/settings_private_event_router.h b/chrome/browser/extensions/api/settings_private/settings_private_event_router.h
index 75fef8f2c4505e238e79f4ce4dc2898b422ba363..4c2f16667435be57c29fba7e99da71b20bd964d2 100644
--- a/chrome/browser/extensions/api/settings_private/settings_private_event_router.h
+++ b/chrome/browser/extensions/api/settings_private/settings_private_event_router.h
@@ -8,6 +8,7 @@
 #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"
@@ -55,6 +56,9 @@ class SettingsPrivateEventRouter : public KeyedService,
 
   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 =
@@ -67,6 +71,8 @@ class SettingsPrivateEventRouter : public KeyedService,
 
   std::unique_ptr<PrefsUtil> prefs_util_;
 
+  base::WeakPtrFactory<SettingsPrivateEventRouter> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(SettingsPrivateEventRouter);
 };