Since https://crrev.com/c/712734, this struct is not being used any
more.

R=titzer@chromium.org

Change-Id: I5b7a73e99ef50fa4fd0f05f6e2b97fa54ea19f1d
Reviewed-on: https://chromium-review.googlesource.com/738033Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48939}