Implement StructTraits for various cc and gpu types

gpu/ipc/common/sync_token.mojom

 // 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.
 
 module gpu.mojom;
 
-[Native]
-struct SyncToken;
+// See gpu/command_buffer/common/constants.h
+enum CommandBufferNamespace {
+  INVALID = -1,
+
+  GPU_IO,
+  IN_PROCESS,
+  MOJO,
+  MOJO_LOCAL,
+
+  NUM_COMMAND_BUFFER_NAMESPACES
+};
+
+// See gpu/command_buffer/common/sync_token.h
+struct SyncToken {
+  bool verified_flush;
+  CommandBufferNamespace namespace_id;
+  int32 extra_data_field;
+  uint64 command_buffer_id;
+  uint64 release_count;
+};