add FilterLevel API to SkPaint, replacing various Flag bits

BUG=
R=bsalomon@google.com

Review URL: https://codereview.chromium.org/19769005

git-svn-id: http://skia.googlecode.com/svn/trunk@10138 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed