Add distance values to interior of filled RRects

This doesn't compute the correct distance vector but it suffices for gaussian edges.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2986

Change-Id: I8bd9e37b0f3788c30d85c95a3c0845d093f22554
Reviewed-on: https://skia-review.googlesource.com/2986
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
3 files changed