Convert //chrome/browser/sync_file_system from scoped_ptr to std::unique_ptr

chrome/browser/sync_file_system/drive_backend/callback_tracker.cc

Index: chrome/browser/sync_file_system/drive_backend/callback_tracker.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/callback_tracker.cc b/chrome/browser/sync_file_system/drive_backend/callback_tracker.cc
index b036c0617d50d93799c8fd63aba2656c5ad607a5..e5dc5c51631271da8acdba7699a9c1e09520c3f4 100644
--- a/chrome/browser/sync_file_system/drive_backend/callback_tracker.cc
+++ b/chrome/browser/sync_file_system/drive_backend/callback_tracker.cc
@@ -26,10 +26,10 @@ void CallbackTracker::AbortAll() {
   }
 }
 
-scoped_ptr<internal::AbortHelper> CallbackTracker::PassAbortHelper(
+std::unique_ptr<internal::AbortHelper> CallbackTracker::PassAbortHelper(
     internal::AbortHelper* helper) {
   if (helpers_.erase(helper) == 1)
-    return scoped_ptr<internal::AbortHelper>(helper);
+    return std::unique_ptr<internal::AbortHelper>(helper);
   return nullptr;
 }