This fixes another Linux compile error in the EGL layer.

BUG=angle:773

Change-Id: Iba643a72fb7b0d5994fe69e46184256e07aa3aad
Reviewed-on: https://chromium-review.googlesource.com/232945Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>