Name 'client' parameter so comment makes sense

Feedback from https://skia-review.googlesource.com/c/14192/

Bug: skia:
Change-Id: I8f1f1b57aabb37c476d244414b3b2fa8693594bd
Reviewed-on: https://skia-review.googlesource.com/14266
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed