fixed iOS build failure

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4997

Change-Id: I5c3727c5dc0e30ae88e1879e12547bdb11db97ee
Reviewed-on: https://skia-review.googlesource.com/4997
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
2 files changed