GpuVSyncProvider with unit test

gpu/ipc/service/gpu_vsync_provider.h

Index: gpu/ipc/service/gpu_vsync_provider.h
diff --git a/gpu/ipc/service/gpu_vsync_provider.h b/gpu/ipc/service/gpu_vsync_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..13d0ac210a1fc96b1961e0c94bee62039e3e6f32
--- /dev/null
+++ b/gpu/ipc/service/gpu_vsync_provider.h
@@ -0,0 +1,48 @@
+// Copyright (c) 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_SERVICE_GPU_VSYNC_PROVIDER_H_
+#define GPU_IPC_SERVICE_GPU_VSYNC_PROVIDER_H_
+
+#include <memory>
+
+#include "base/callback.h"
+#include "base/time/time.h"
+#include "gpu/gpu_export.h"
+#include "gpu/ipc/common/surface_handle.h"
+
+namespace gpu {
+
+class GpuVSyncWorker;
+
+// Implements waiting for VSync signal on background thread.
+class GPU_EXPORT GpuVSyncProvider {
+ public:
+  // Once VSync is enabled, this callback is repeatedly invoked on every VSync.
+  // The call is made on background thread to avoid increased latency due to
+  // serializing callback invocation with other GPU tasks. The code that
+  // implements the callback function is expected to handle that.
+  using VSyncCallback = base::Callback<void(base::TimeTicks timestamp)>;
+
+  ~GpuVSyncProvider();
+
+  static std::unique_ptr<GpuVSyncProvider> Create(const VSyncCallback& callback,
+                                                  SurfaceHandle surface_handle);
+
+  // Enable or disable VSync production.
+  void EnableVSync(bool enabled);
+
+ private:
+#if defined(OS_WIN)
+  GpuVSyncProvider(const VSyncCallback& callback, SurfaceHandle surface_handle);
+
+  std::unique_ptr<GpuVSyncWorker> vsync_worker_;
+#endif  // defined(OS_WIN)
+
+  DISALLOW_COPY_AND_ASSIGN(GpuVSyncProvider);
+};
+
+}  // namespace gpu
+
+#endif  // GPU_IPC_SERVICE_GPU_VSYNC_PROVIDER_H_