use quads for mixed radius rrects

Create a specialized version of adding a pair of corner quads
that avoids the overhead of the full arc machinery.

This is on the way to changing Chrome to calling Skia directly to create fully general round rects rather than rolling their own.

R=robertphillips@google.com, reed@google.com

Author: caryclark@google.com

Review URL: https://codereview.chromium.org/60203002

git-svn-id: http://skia.googlecode.com/svn/trunk/src@12190 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed