Turn clear-to-white-then-intersect clips into clear-to-black-then-replace

Turn clear-to-white-then-intersect clips into clear-to-black-then-replace

R=robertphillips@google.com

Committed: http://code.google.com/p/skia/source/detail?r=11786

[brian1, 2013-10-15 18:50:11]

This causes a few lsb differences in some GMs, but otherwise draws the same.

[robertphillips, 2013-10-15 18:52:14]

lgtm

[commit-bot: I haz the power, 2013-10-15 18:59:24]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/bsalomon@google.com/27170003/1

[commit-bot: I haz the power, 2013-10-15 20:04:09]

Change committed as 11786