path ops near exact

Modify line intersections to first
- match exact ends
- compute intersections
- match near ends
where the exact ends are preferred, then near matches, then
computed matches. This pulls matches towards existing end points
when possible, and keeps intersection distances consistent with
different line/line line/quad and line/cubic computations.

BUG=

Review URL: https://codereview.chromium.org/19183003

git-svn-id: http://skia.googlecode.com/svn/trunk@10073 2bbb7eff-a529-9590-31e7-b0007b416f81
29 files changed