Speeup hairline curves (quads and cubics)

/skia/trunk> cat ../old.txt
maxrss	loops	min	median	mean	max	stddev	samples   	config	bench
   9M	1	4.28ms	4.32ms	4.36ms	4.67ms	3%	▄▁▁▃▂▂▁▁▂█	8888	path_hairline_small_AA_cubic
   9M	1	743µs	767µs	770µs	825µs	4%	▃▃▇▃▁▁▅▁█▁	8888	path_hairline_small_AA_conic
   9M	1	533µs	606µs	598µs	680µs	9%	▁▂▂█▆▇▇▄▂▂	8888	path_hairline_small_AA_quad
   9M	1	451µs	452µs	456µs	495µs	3%	▁▁▁▁█▁▁▁▁▁	8888	path_hairline_small_AA_line

/skia/trunk> cat ../new.txt
maxrss	loops	min	median	mean	max	stddev	samples   	config	bench
   9M	1	827µs	827µs	831µs	869µs	2%	▁▁▁▁▁▁▁█▁▁	8888	path_hairline_small_AA_cubic
   9M	1	515µs	517µs	517µs	518µs	0%	▇█▆▅▃▃▁▁▁▅	8888	path_hairline_small_AA_conic
   9M	1	310µs	311µs	315µs	332µs	2%	▂▁█▆▁▁▁▁▁▁	8888	path_hairline_small_AA_quad
   9M	1	254µs	254µs	258µs	276µs	3%	▁▁▁▁▁▁▁█▇▂	8888	path_hairline_small_AA_line

Edited revert of https://codereview.chromium.org/1085013003

TBR=

Review URL: https://codereview.chromium.org/1078413003
6 files changed