Reland "Intersection calc cleanup."

This is a reland of 1b016d50b9023c5c2953666aed76b096d56e3dc0

Original change's description:
> Intersection calc cleanup.
> 
> * Fixes some bugs in compute_intersection
> * Adds an intersection check that doesn't need to compute the exact pt
> * Make some of the variable names consistent
> * General floating point tweaks
> 
> Bug: skia:
> Change-Id: Ib2fb8bee39b5d9c635d62e606fe826b7efe64dfa
> Reviewed-on: https://skia-review.googlesource.com/145532
> Commit-Queue: Jim Van Verth <jvanverth@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Bug: skia:
Change-Id: I3fe00add6f700b58fd756b9fbb24078e010ed9ba
Reviewed-on: https://skia-review.googlesource.com/145920
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
2 files changed