Avoid infinite loop in Codec_requiredFrame test

Prior to this commit, the test would finish (and pass) with a correct
SkCodec implementation, but could infinite loop (instead of finish with
failure) with an incorrect implementation.

Bug: skia:
Change-Id: I89e8cfef9837c50e83a23e67a40204a9478a17cb
Reviewed-on: https://skia-review.googlesource.com/144740
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
1 file changed