add new blit2 methods in support of antialiased hairlines

before:
   9M	1	528µs	530µs	539µs	607µs	5%	▁▁▁▁▁▁▁▁█▂	8888	path_hairline_small_AA_quad

after:
   9M	1	355µs	356µs	358µs	375µs	2%	▂▁▁▁▁▁▁▁▁█	8888	path_hairline_small_AA_quad

BUG=skia:

does require new baselines (bug chrome is guarded)

Review URL: https://codereview.chromium.org/1060153003
4 files changed