This broke the Linux standalone build. Error message seen when running
"gclient runhooks":

"gyp: name 'use_ozone' is not defined while evaluating condition
'OS=="linux" and use_ozone==0' in build/ANGLE.gyp while trying to load
build/ANGLE.gyp"

This reverts commit 35e65e92.

Change-Id: Iee5f08195ee1c74ead99bb9d70d04928c9bae7af
Reviewed-on: https://chromium-review.googlesource.com/338290Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>