Reland: Added SyncToken command buffer trait to help with IPC messages

gpu/command_buffer/service/mailbox_manager_unittest.cc

Index: gpu/command_buffer/service/mailbox_manager_unittest.cc
diff --git a/gpu/command_buffer/service/mailbox_manager_unittest.cc b/gpu/command_buffer/service/mailbox_manager_unittest.cc
index 5101604a3687369c2be85c3b00888def013583a9..81979d098fa2faa6a1820716f584f3f377a0ea27 100644
--- a/gpu/command_buffer/service/mailbox_manager_unittest.cc
+++ b/gpu/command_buffer/service/mailbox_manager_unittest.cc
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "gpu/command_buffer/common/sync_token.h"
 #include "gpu/command_buffer/service/feature_info.h"
 #include "gpu/command_buffer/service/gpu_service_test.h"
 #include "gpu/command_buffer/service/mailbox_manager_impl.h"
@@ -17,8 +18,9 @@ namespace gles2 {
 
 using namespace ::testing;
 
-static const SyncToken g_sync_token = {gpu::CommandBufferNamespace::GPU_IO, 123,
-                                       0};
+static const SyncToken g_sync_token(gpu::CommandBufferNamespace::GPU_IO,
+                                    123,
+                                    0);
 
 class MailboxManagerTest : public GpuServiceTest {
  public: