Revert "New read pixels implementation that is simpler but does all conversions on CPU."

This reverts commit c9a642edf2d1c7f5380fe829adbb1a692f9969a6.

Reason for revert: 1010102 gms broke

Original change's description:
> New read pixels implementation that is simpler but does all conversions on CPU.
> 
> Change-Id: Ia548cd24a8544b35a233311706faf48de353b7cf
> Reviewed-on: https://skia-review.googlesource.com/109902
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>

TBR=bsalomon@google.com,robertphillips@google.com,brianosman@google.com

Change-Id: I7724a6eef79885ba2a32c1ac871e5b2a9a3c0c12
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/115140
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
18 files changed