The path ops builder code needs to determine the winding of each contour added, and...

The path ops builder code needs to determine the winding of each contour added, and reverse windings if the contours are nested in other contours.

Cheap (one contour) paths can be evaluated and reversed as needed with a minimum of checking, but multi-contour paths invoke the regular path ops machinery to determine who is contained by whom.

More tests need to be added to verify that all corner cases are considered, but this fixes the cases in the bug thus far.

R=fmalita@chromium.org
TBR=reed@google.com
BUG=skia:3838

Review URL: https://codereview.chromium.org/1129193006