[SyncFS] Use nullptr for scoped_ptr initialization

chrome/browser/sync_file_system/sync_file_system_service.cc

Index: chrome/browser/sync_file_system/sync_file_system_service.cc
diff --git a/chrome/browser/sync_file_system/sync_file_system_service.cc b/chrome/browser/sync_file_system/sync_file_system_service.cc
index a8f47a0fc7c382e041ac3e3f8dc9c47cfbd1f214..448b69912f631f8882dc46ea05e69fd3456fb43f 100644
--- a/chrome/browser/sync_file_system/sync_file_system_service.cc
+++ b/chrome/browser/sync_file_system/sync_file_system_service.cc
@@ -146,7 +146,8 @@ class LocalSyncRunner : public SyncProcessRunner,
   LocalSyncRunner(const std::string& name,
                   SyncFileSystemService* sync_service)
       : SyncProcessRunner(name, sync_service,
-                          scoped_ptr<SyncProcessRunner::TimerHelper>(), 1),
+                          nullptr,  /* timer_helper */
+                          1  /* max_parallel_task */),
         factory_(this) {}
 
   virtual void StartSync(const SyncStatusCallback& callback) OVERRIDE {
@@ -189,7 +190,8 @@ class RemoteSyncRunner : public SyncProcessRunner,
                    SyncFileSystemService* sync_service,
                    RemoteFileSyncService* remote_service)
       : SyncProcessRunner(name, sync_service,
-                          scoped_ptr<SyncProcessRunner::TimerHelper>(), 1),
+                          nullptr,  /* timer_helper */
+                          1  /* max_parallel_task */),
         remote_service_(remote_service),
         last_state_(REMOTE_SERVICE_OK),
         factory_(this) {}