ui: Add libsync GLFence implementation.

gpu/ipc/client/gpu_fence_impl_libsync.h

+// Copyright 2016 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 GPU_IPC_CLIENT_GPU_FENCE_IMPL_LIBSYNC_H_
+#define GPU_IPC_CLIENT_GPU_FENCE_IMPL_LIBSYNC_H_
+
+#include "base/files/scoped_file.h"
+#include "gpu/gpu_export.h"
+#include "gpu/ipc/client/gpu_fence_impl.h"
+
+namespace gpu {
+
+class GPU_EXPORT GpuFenceImplLibsync : public GpuFenceImpl {
+ public:
+  explicit GpuFenceImplLibsync(const base::FileDescriptor& fd);
+  ~GpuFenceImplLibsync() override;
+
+  // Overridden from gfx::GpuFence:
+  bool IsSignaled() override;
+  bool Wait(const base::TimeDelta& max_time) override;
+  gfx::GpuFenceHandle GetHandle() const override;
+
+ private:
+  base::ScopedFD fd_;
+
+  DISALLOW_COPY_AND_ASSIGN(GpuFenceImplLibsync);
+};
+
+}  // namespace gpu
+
+#endif  // GPU_IPC_CLIENT_GPU_FENCE_IMPL_LIBSYNC_H_