Revert "Disallow readPixels() conversions from untagged srcs to tagged dsts"

This reverts commit ccfd1083a7b9d546735ddd1037f3240635cce72d.

Reason for revert: Roll is failing.

Original change's description:
> Disallow readPixels() conversions from untagged srcs to tagged dsts
> 
> This might break the roll into Chrome.  But let's see how.
> 
> BUG=skia:6021
> 
> Change-Id: I2698b5d6fe72d01bed0dc64703b592a03d441a80
> Reviewed-on: https://skia-review.googlesource.com/7127
> Reviewed-by: Mike Reed <reed@google.com>
> Commit-Queue: Matt Sarett <msarett@google.com>
> 

TBR=msarett@google.com,brianosman@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:6021

Change-Id: I4b62178fd7c23f43cf69ca69fc14526ecd503956
Reviewed-on: https://skia-review.googlesource.com/7205
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
2 files changed