turn assert into check for text

Bug: skia:7425
Change-Id: Ica173122dbe3cd1a3f94b2880a77c7e8b7e9cc8e
Reviewed-on: https://skia-review.googlesource.com/96640
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed