Relax matrix check for fast case in rect blur shader

Was checking scale+translate but that was overly strict.

Bug: chromium:1087705
Change-Id: I19c54eab9baffac21cfaf4ef781a60566a39f666
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/319779
Commit-Queue: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
3 files changed