skpbench: add option for gpu timing

tools/gpu/FenceSync.h

Index: tools/gpu/FenceSync.h
diff --git a/tools/gpu/FenceSync.h b/tools/gpu/FenceSync.h
index 8f2bbe2e8617930341106405b753e9ccd227cdcd..b430f5dfa9b94c3f5c712bff387121ec6b1280b3 100644
--- a/tools/gpu/FenceSync.h
+++ b/tools/gpu/FenceSync.h
@@ -13,7 +13,7 @@
 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
@@ -29,6 +29,6 @@ public:
     virtual ~FenceSync() {}
 };
 
-}
+}  // namespace sk_gpu_test
 
 #endif