Added missing quotes.

BUG=angleproject:2297

Change-Id: Ieb6ca4ae37786f48ad3c6f5dccefef25afce23a2
Reviewed-on: https://chromium-review.googlesource.com/852636Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>