[Sync] Add support for immediately enabling wallet datatype

chrome/browser/sync/glue/autofill_wallet_data_type_controller.h

Index: chrome/browser/sync/glue/autofill_wallet_data_type_controller.h
diff --git a/chrome/browser/sync/glue/autofill_wallet_data_type_controller.h b/chrome/browser/sync/glue/autofill_wallet_data_type_controller.h
index e5381dec9f8eaa439fe6533825aaa33fcbbcde01..a652f6dadf92806a050ab6e39d348b53891ee55a 100644
--- a/chrome/browser/sync/glue/autofill_wallet_data_type_controller.h
+++ b/chrome/browser/sync/glue/autofill_wallet_data_type_controller.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_SYNC_GLUE_AUTOFILL_WALLET_DATA_TYPE_CONTROLLER_H_
 
 #include "base/basictypes.h"
+#include "base/prefs/pref_change_registrar.h"
 #include "components/sync_driver/non_ui_data_type_controller.h"
 
 class Profile;
@@ -33,12 +34,19 @@ class AutofillWalletDataTypeController
                                const base::Closure& task) override;
   bool StartModels() override;
   void StopModels() override;
+  bool ReadyForStart() const override;
 
   void WebDatabaseLoaded();
 
+  // Callback for changes to kAutofillWalletSyncExperimentEnabled.
+  void OnSyncExperimentPrefChanged();
+
   Profile* const profile_;
   bool callback_registered_;
 
+  // Registrar for listening to kAutofillWalletSyncExperimentEnabled status.
+  PrefChangeRegistrar pref_registrar_;
+
   DISALLOW_COPY_AND_ASSIGN(AutofillWalletDataTypeController);
 };