Revert "Factor out common code from sweep and linear."

This reverts commit b7a330ff0048875e178b2d9a68cd5605d83baf8d.

Reason for revert: Oof, I hate to do this, but we didn't expect this to change any drawing did we?  This draws a bunch of GMs differently in both 565 and sRGB mode, some very noticeably.

Original change's description:
> Factor out common code from sweep and linear.
> 
> And, some file cleanup.
> 
> Change-Id: I804db924bce3b5834f6cda481315dd2da38df5ca
> Reviewed-on: https://skia-review.googlesource.com/15226
> Commit-Queue: Herb Derby <herb@google.com>
> Reviewed-by: Mike Klein <mtklein@chromium.org>
> Reviewed-by: Florin Malita <fmalita@chromium.org>
> 

TBR=mtklein@chromium.org,mtklein@google.com,herb@google.com,fmalita@chromium.org,fmalita@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I75bb6c3e4045a0f70c7e9552b84b22f0fed73b80
Reviewed-on: https://skia-review.googlesource.com/15464
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
8 files changed