Move GPU fences into sk_gpu_test

include/private/SkGpuFenceSync.h

-
-/*
- * Copyright 2015 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-#ifndef SkGpuFenceSync_DEFINED
-#define SkGpuFenceSync_DEFINED
-
-#include "SkTypes.h"
-
-typedef void* SkPlatformGpuFence;
-constexpr static SkPlatformGpuFence kInvalidPlatformGpuFence = nullptr;
-
-/*
- * 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 SkGpuFenceSync {
-public:
-    virtual SkPlatformGpuFence SK_WARN_UNUSED_RESULT insertFence() const = 0;
-    virtual bool waitFence(SkPlatformGpuFence) const = 0;
-    virtual void deleteFence(SkPlatformGpuFence) const = 0;
-
-    virtual ~SkGpuFenceSync() {}
-};
-
-#endif