Make haveDecodedRow return void

The method already always returns true, except in a single case after
asserting.

Change-Id: Icf241a8af04220d459c0782ffd9b74c34c753236
Reviewed-on: https://skia-review.googlesource.com/37161
Reviewed-by: Chris Blume <cblume@chromium.org>
Commit-Queue: Leon Scroggins <scroggo@google.com>
4 files changed