Validate SkSpecialSurface raster info

BUG=chromium:716311

Change-Id: I01ea2e77ba8920f735395dd46ef2cea78a858308
Reviewed-on: https://skia-review.googlesource.com/15230
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
3 files changed