Revert "Respect full precision for RGB16 PNGs"

This reverts commit 7a090c403da1dad6a2e19f2011158bd894a62d91.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Respect full precision for RGB16 PNGs
> 
> BUG=skia:
> 
> CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD
> 
> Change-Id: If58d201daae97bce2f8efbc453c2ec452e682493
> Reviewed-on: https://skia-review.googlesource.com/7085
> Commit-Queue: Matt Sarett <msarett@google.com>
> Reviewed-by: Mike Klein <mtklein@chromium.org>
> Reviewed-by: Leon Scroggins <scroggo@google.com>
> Reviewed-by: Mike Reed <reed@google.com>
> 

TBR=mtklein@chromium.org,mtklein@google.com,msarett@google.com,scroggo@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:
CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD

Change-Id: Ibd9879bc4f65ca0c2457dd0bfb5eb008d9a8f672
Reviewed-on: https://skia-review.googlesource.com/7183
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
12 files changed