[Sync] Migrate SyncInternalsMessageHandler off CallJavascriptFunctionUnsafe.

components/sync/driver/sync_service_base.h

 // Copyright 2016 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 COMPONENTS_SYNC_DRIVER_SYNC_SERVICE_BASE_H_
 #define COMPONENTS_SYNC_DRIVER_SYNC_SERVICE_BASE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 29 matching lines @@
                   std::unique_ptr<SigninManagerWrapper> signin,
                   const version_info::Channel& channel,
                   const base::FilePath& base_directory,
                   const std::string& debug_identifier);
   ~SyncServiceBase() override;
 
   // SyncService partial implementation.
   void AddObserver(SyncServiceObserver* observer) override;
   void RemoveObserver(SyncServiceObserver* observer) override;
   bool HasObserver(const SyncServiceObserver* observer) const override;
+  SigninManagerBase* signin() const override;
 
   // Given base path (path to profile) formats path to "Sync Data" folder where
   // sync engine stores directory database.
   static base::FilePath FormatSyncDataPath(
       const base::FilePath& base_directory);
 
   // Given base path (path to profile) formats path to a folder containing
   // ModelTypeStore's leveldb database.
   static base::FilePath FormatSharedModelTypeStorePath(
       const base::FilePath& base_directory);
@@ skipping 65 matching lines @@
   // this object was created on.
   base::ThreadChecker thread_checker_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SyncServiceBase);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_SYNC_SERVICE_BASE_H_