Allow SkChopCubicAt to have the same src and dst

Also updates SkConvertQuadToCubic to do the same.

Bug: skia:
Change-Id: Id1da5182b0696492ca9c8e99243cb86fbdbfcd2f
Reviewed-on: https://skia-review.googlesource.com/146212
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
1 file changed