skpbench: add option for gpu timing

tools/gpu/FenceSync.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef FenceSync_DEFINED
 #define FenceSync_DEFINED
 
 #include "SkTypes.h"
 
 namespace sk_gpu_test {
 
 using PlatformFence = uint64_t;
-static constexpr PlatformFence kInvalidPlatformFence = 0;
+static constexpr PlatformFence kInvalidFence = 0;
 
 /*
  * This class provides an interface to interact with fence syncs. A fence sync is an object that the
  * client can insert into the GPU command stream, and then at any future time, wait until all
  * commands that were issued before the fence have completed.
  */
 class FenceSync {
 public:
     virtual PlatformFence SK_WARN_UNUSED_RESULT insertFence() const = 0;
     virtual bool waitFence(PlatformFence) const = 0;
     virtual void deleteFence(PlatformFence) const = 0;
 
     virtual ~FenceSync() {}
 };
 
-}
+}  // namespace sk_gpu_test
 
 #endif