Add internal tree implementation to EdgeList.

Makes some of the intersection and comparison calculations more
robust and faster as well.

Bug: skia:
Change-Id: Ic6b6599be185d4fd888899ecd02ba0df7bc33e18
Reviewed-on: https://skia-review.googlesource.com/146383
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed