reland: use the defined preprocessor function.

BUG=angleproject:1044

Change-Id: I6171708a2d55ec085ba2c598a1a863779842da6c
Reviewed-on: https://chromium-review.googlesource.com/311270
Tryjob-Request: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>