Add validation of RRects to SkValidatingReadBuffer

This comes from the Skia fuzzer where it is inverting the RRect's rect which causes trouble down the line.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2591

Change-Id: I5c34105a47369492d2df99d39a4e29116060ad37
Reviewed-on: https://skia-review.googlesource.com/2591
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
3 files changed