[SyncFS] Use variadic template in callback_tracker_internal.h

chrome/browser/sync_file_system/drive_backend/callback_tracker_internal.h.pump

-$$ This is a pump file for generating file templates.  Pump is a python
-$$ script that is part of the Google Test suite of utilities.  Description
-$$ can be found here:
-$$
-$$ http://code.google.com/p/googletest/wiki/PumpManual
-$$
-$$ See comment for MAX_ARITY in base/bind.h.pump.
-$var MAX_ARITY = 7
-
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_CALLBACK_TRACKER_INTERNAL_H_
-#define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_CALLBACK_TRACKER_INTERNAL_H_
-
-#include "base/callback.h"
-#include "base/callback_internal.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/weak_ptr.h"
-
-namespace sync_file_system {
-namespace drive_backend {
-
-class CallbackTracker;
-
-namespace internal {
-
-class AbortHelper {
- public:
-  explicit AbortHelper(CallbackTracker* tracker);
-  ~AbortHelper();
-  base::WeakPtr<AbortHelper> AsWeakPtr();
-
-  static scoped_ptr<AbortHelper> TakeOwnership(
-      const base::WeakPtr<AbortHelper>& abort_helper);
-
- private:
-  CallbackTracker* tracker_;  // Not owned.
-  base::WeakPtrFactory<AbortHelper> weak_ptr_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(AbortHelper);
-};
-
-template <typename>
-struct InvokeAndInvalidateHelper;
-
-$range ARITY 0..MAX_ARITY
-$for ARITY [[
-$range ARG 1..ARITY
-
-template <$for ARG , [[typename A$(ARG)]]>
-struct InvokeAndInvalidateHelper<void($for ARG , [[A$(ARG)]])> {
-  static void Run(const base::WeakPtr<AbortHelper>& abort_helper,
-                  const base::Callback<void($for ARG , [[A$(ARG)]])>& callback
-$if ARITY != 0 [[, ]]
-$for ARG , [[A$(ARG) a$(ARG)]]
-) {
-    scoped_ptr<AbortHelper> deleter = AbortHelper::TakeOwnership(abort_helper);
-    if (deleter) {
-      callback.Run(
-$for ARG , [[base::internal::CallbackForward(a$(ARG))]]);
-    }
-  }
-};
-
-]]  $$ for ARITY
-
-}  // namespace internal
-}  // namespace drive_backend
-}  // namespace sync_file_system
-
-#endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_CALLBACK_TRACKER_INTERNAL_H_