remove legacy filter-flags, and store FilterLevel directly

BUG=skia:
R=robertphillips@google.com, humper@google.com, jvanverth@google.com, mtklein@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/239393002

git-svn-id: http://skia.googlecode.com/svn/trunk@14217 2bbb7eff-a529-9590-31e7-b0007b416f81
7 files changed