ui: Add libsync GLFence implementation.

gpu/ipc/client/gpu_channel_host.cc

Index: gpu/ipc/client/gpu_channel_host.cc
diff --git a/gpu/ipc/client/gpu_channel_host.cc b/gpu/ipc/client/gpu_channel_host.cc
index c44cd9ac61b3439a19bd111af9d935aca73002a7..850eaa30ed640e88d178d6ad97e5385035925a18 100644
--- a/gpu/ipc/client/gpu_channel_host.cc
+++ b/gpu/ipc/client/gpu_channel_host.cc
@@ -286,8 +286,16 @@ int32_t GpuChannelHost::ReserveImageId() {
 gfx::GpuFenceHandle GpuChannelHost::ShareGpuFenceToGpuProcess(
     const gfx::GpuFenceHandle& source_handle) {
   gfx::GpuFenceHandle handle;
-  handle.shared_event_handle =
-      gfx::SharedEvent::DuplicateHandle(source_handle.shared_event_handle);
+  if (gfx::SharedEvent::IsHandleValid(source_handle.shared_event_handle)) {
+    handle.shared_event_handle =
+        gfx::SharedEvent::DuplicateHandle(source_handle.shared_event_handle);
+  }
+#if defined(OS_LINUX)
+  if (source_handle.fd.fd >= 0) {
+    handle.fd.fd = HANDLE_EINTR(dup(source_handle.fd.fd));
+    handle.fd.auto_close = true;
+  }
+#endif
   return handle;
 }