ui: Add libsync GLFence implementation.

ui/gfx/gpu_fence.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 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"
 
+#if defined(OS_LINUX)
+#include "base/file_descriptor_posix.h"
+#endif
+
 extern "C" typedef struct _ClientFence* ClientFence;
 
 namespace gfx {
 
 struct GFX_EXPORT GpuFenceHandle {
   SharedEventHandle shared_event_handle;
+#if defined(OS_LINUX)
+  base::FileDescriptor fd;
+#endif
 };
 
 // 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;
@@ skipping 10 matching lines @@
   // 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_