Added an extra sync token field for extra command buffer identification.

gpu/command_buffer/tests/gl_manager.cc

Index: gpu/command_buffer/tests/gl_manager.cc
diff --git a/gpu/command_buffer/tests/gl_manager.cc b/gpu/command_buffer/tests/gl_manager.cc
index 0c351e844318d27533979cd4a74d9739a5215471..2eff3a95365eabd544bac42013e181d10e51b274 100644
--- a/gpu/command_buffer/tests/gl_manager.cc
+++ b/gpu/command_buffer/tests/gl_manager.cc
@@ -509,6 +509,10 @@ uint64_t GLManager::GetCommandBufferID() const {
   return command_buffer_id_;
 }
 
+uint32_t GLManager::GetExtraCommandBufferData() const {
+  return 0;
+}
+
 uint64_t GLManager::GenerateFenceSyncRelease() {
   return next_fence_sync_release_++;
 }