Start to unify signatures: return bool

Change-Id: If4a8e06f3a176697e3f5136dfc7ab1fbb347da70
Bug: skia:8937
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/205120
Reviewed-by: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
15 files changed