ccpr: Update the sample to use proper coverage count buffers

Bug: skia:
Change-Id: I6ce3ec567e671fa2ab3f05403015b48251518227
Reviewed-on: https://skia-review.googlesource.com/115072
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
5 files changed