Revert "more powerful map()"

This reverts commit a3dd5ec3a769fb833ce77878cd4e551c15e5074d.

Reason for revert: breaks -Fast bot

Original change's description:
> more powerful map()
> 
> Change-Id: Icbae002999a295e3a9d1d2e6046e686784d5f608
> Reviewed-on: https://skia-review.googlesource.com/69901
> Reviewed-by: Florin Malita <fmalita@chromium.org>
> Commit-Queue: Mike Klein <mtklein@chromium.org>

TBR=mtklein@chromium.org,fmalita@chromium.org

Change-Id: I536f3eb8d8d3e39f38583403a2350a082185f6ee
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/70106
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>