Remove SkBaseDevice::flush

Another small step in removing SkCanvas::flush

Change-Id: I6f17edcd1996e1009dad7cc96a97be3b0c4664f4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/334417
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Adlai Holler <adlai@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
8 files changed