Revert 266381 "content: Add missing IPC traits for sync_query."

This appears to have introduced assertion failures on the
linux_gpu_triggered_tests try server -- and would have done so on the
Linux Debug (NVIDIA) bot, too, if the hardware had not failed late
last week.

Links to the failures have been added to crbug.com/269808.

> content: Add missing IPC traits for sync_query.
> 
> R=cdn@chromium.org, piman@chromium.org
> BUG=269808
> 
> Review URL: https://codereview.chromium.org/250803010

TBR=reveman@chromium.org

Review URL: https://codereview.chromium.org/252833003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266454 0039d316-1c4b-4281-b951-d872f2087c98

content/common/gpu/gpu_messages.h

@@ -197,7 +197,6 @@ IPC_STRUCT_TRAITS_BEGIN(gpu::Capabilities)
   IPC_STRUCT_TRAITS_MEMBER(texture_usage)
   IPC_STRUCT_TRAITS_MEMBER(texture_storage)
   IPC_STRUCT_TRAITS_MEMBER(discard_framebuffer)
-  IPC_STRUCT_TRAITS_MEMBER(sync_query)
   IPC_STRUCT_TRAITS_MEMBER(map_image)
 IPC_STRUCT_TRAITS_END()