Cosmetic portion of reverted "Fix ClipMaskManager's SW-fallback logic" CL

This CL isolates the cosmetic portion so the functional portion is clearer. It relies on https://codereview.chromium.org/1412883005/ (Fix ClipMaskManager's SW-fallback logic (take 2))

Review URL: https://codereview.chromium.org/1422023003
6 files changed