Fix for Ovals/RRects on N4 missing interior rectangles.

Clamp square of gradiant length to non-zero value so it can be passed to
inversesqrt().
Also adds some fixes to rrect setup to avoid crossing zero.

Skia issue #1372

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

Review URL: https://codereview.chromium.org/18375003

git-svn-id: http://skia.googlecode.com/svn/trunk@9864 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed