gpu: Add GpuFence framework.

ui/gfx/gpu_fence.h

Index: ui/gfx/gpu_fence.h
diff --git a/ui/gfx/gpu_fence.h b/ui/gfx/gpu_fence.h
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+++ b/ui/gfx/gpu_fence.h
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+// 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 UI_GFX_GPU_FENCE_H_
+#define UI_GFX_GPU_FENCE_H_
+
+#include "base/time/time.h"
+#include "ui/gfx/gfx_export.h"
+#include "ui/gfx/shared_event.h"
+
+extern "C" typedef struct _ClientFence* ClientFence;
+
+namespace gfx {
+
+struct GFX_EXPORT GpuFenceHandle {
+  SharedEventHandle shared_event_handle;
+};
+
+// This interface correspond to a type of fence that can be shared between
+// processes and signaled by the GPU.
+class GFX_EXPORT GpuFence {
+ public:
+  virtual ~GpuFence() {}
+
+  // Returns true if the fence is in the signaled state, else false.
+  virtual bool IsSignaled() = 0;
+
+  // Wait up until max_time has passed for the fence to be signaled. Returns
+  // true if the fence was signaled. If this method returns false, then it
+  // does not necessarily mean that |max_time| was exceeded.
+  virtual bool Wait(const base::TimeDelta& max_time) = 0;
+
+  // Reset that state of fence to 'unsignaled'. Calling this when the fence
+  // is not 'signaled' is an error.
+  virtual void Reset() = 0;
+
+  // Returns a platform specific handle for this fence.
+  virtual GpuFenceHandle GetHandle() const = 0;
+
+  // Type-checking downcast routine.
+  virtual ClientFence AsClientFence() = 0;
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_GPU_FENCE_H_