This is disallowed in Chromium because it isn't currently portable.
We can put it back later if the rules change.

BUG=angleproject:956

Change-Id: I5be28590f494719b8cc995739dde26726283fced
Reviewed-on: https://chromium-review.googlesource.com/262777Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>