Revert "Use SDF path miplevels based on the original path's size."

Revert "Use SDF path miplevels based on the original path's size."

This reverts commit 6e83b13c226246041a33dc7bf0e92626581b5e79.

Reason for revert: Fractional path sizes are causing asserts on the bots.

Original change's description:
> Use SDF path miplevels based on the original path's size.
>
> Should produce sharper results than arbitrary fixed sizes.
> Adds a new test to pathfill GM.
>
> BUG=chromium:682918
>
> Change-Id: I5a394098665d01e995a244fde278236f1471e6c9
> Reviewed-on: https://skia-review.googlesource.com/8328
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Jim Van Verth <jvanverth@google.com>
>

TBR=jvanverth@google.com,bsalomon@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:682918

Change-Id: I4a52df808ef3f769d0e6f75785148d46936a6747
Reviewed-on: https://skia-review.googlesource.com/8342
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>