Added SyncToken command buffer trait to help with IPC messages.

gpu/command_buffer/common/sync_token.h

Index: gpu/command_buffer/common/sync_token.h
diff --git a/gpu/command_buffer/common/sync_token.h b/gpu/command_buffer/common/sync_token.h
new file mode 100644
index 0000000000000000000000000000000000000000..380b49dd923474bae9598f29c44a3e1e2528f712
--- /dev/null
+++ b/gpu/command_buffer/common/sync_token.h
@@ -0,0 +1,48 @@
+// Copyright 2015 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_COMMAND_BUFFER_COMMON_SYNC_TOKEN_H_
+#define GPU_COMMAND_BUFFER_COMMON_SYNC_TOKEN_H_
+
+#include <stdint.h>
+
+#include "gpu/command_buffer/common/constants.h"
+#include "gpu/gpu_export.h"
+
+// From glextchromium.h.
+#ifndef GL_SYNC_TOKEN_SIZE_CHROMIUM
+#define GL_SYNC_TOKEN_SIZE_CHROMIUM 24
+#endif
+
+namespace gpu {
+
+// A Sync Token is a binary blob which represents a waitable fence sync
+// on a particular command buffer namespace and id.
+// See src/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt for more
+// details.
+struct GPU_EXPORT SyncToken {
+  using Data = int8_t[GL_SYNC_TOKEN_SIZE_CHROMIUM];
+
+  SyncToken();
+  SyncToken(CommandBufferNamespace namespace_id,
+            uint64_t command_buffer_id,
+            uint64_t release_count);
+
+  CommandBufferNamespace GetNamespaceId() const;
+  uint64_t GetCommandBufferId() const;
+  uint64_t GetReleaseCount() const;
+
+  void SetData(CommandBufferNamespace namespace_id,
+               uint64_t command_buffer_id,
+               uint64_t release_count);
+
+  bool operator<(const SyncToken& other) const;
+
+  Data data;
+};
+
+}  // namespace gpu
+
+#endif  // GPU_COMMAND_BUFFER_COMMON_SYNC_TOKEN_H_
+