Revert "Explicitly fail read/writePixels in invalid color space scenarios"

Revert "Explicitly fail read/writePixels in invalid color space scenarios"

This reverts commit efcc41805b43347444b83c1705d3d60c8d0caa70.

Reason for revert: Possible culprit for Chromium failures.

Original change's description:
> Explicitly fail read/writePixels in invalid color space scenarios
>
> It's not well defined what to do when moving from a nullptr color space to
> a tagged destination (drawing, reading, writing, etc...). In these
> scenarios, at least, we can choose to disallow the operation (rather than
> produce an unexpected or inconsistent result).
>
> BUG=skia:
>
> Change-Id: I033b23c6f2bb00664efc8fdab1b3f52053d77695
> Reviewed-on: https://skia-review.googlesource.com/6600
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Matt Sarett <msarett@google.com>
>

TBR=mtklein@google.com,bsalomon@google.com,msarett@google.com,brianosman@google.com,reviews@skia.org
BUG=skia:
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I17791f9285089ede42b7921324e0dc264865be1d
Reviewed-on: https://skia-review.googlesource.com/6628
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>