Revert "Fix SkImage_Gpu::getROPixels"

Revert "Fix SkImage_Gpu::getROPixels"

This reverts commit f4d443fd1bd8cffbcd7a07a48f3488ae871414e9.

Reason for revert: https://bugs.chromium.org/p/chromium/issues/detail?id=705156

Original change's description:
> Fix SkImage_Gpu::getROPixels
>
> The dstColorSpace is a badly named parameter. It's a hint about where/how
> the returned pixels are going to be used. Raster and GPU are meant to
> ignore that information - codecs use it to drive our decoding heuristic.
>
> I've adopted that name in several places, although it's quite bad. Maybe
> usageColorSpace would be better?
>
> Bug: skia:
> Change-Id: I99acaac4bed57ed8acd8433e1c5b39a60c3af09e
> Reviewed-on: https://skia-review.googlesource.com/10109
> Reviewed-by: Matt Sarett <msarett@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
>

TBR=msarett@google.com,robertphillips@google.com,brianosman@google.com,reed@google.com,reviews@skia.org
# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Id46226e41ca287ef3351710815ae2e842da4d293
Reviewed-on: https://skia-review.googlesource.com/10210
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>