Revert "Access textures via shared images in RasterDecoderImpl::DoCopySubTextureINTERNAL"

This reverts commit a2da080c56b5ec29030010fb1e29dca23f995b7b.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 624913 as the
culprit for failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtL2EyZGEwODBjNTZiNWVjMjkwMzAwMTBmYjFlMjlkY2EyM2Y5OTViN2IM

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.win/Win7%20Tests%20%28dbg%29%281%29/74408

Sample Failed Step: gpu_unittests

Original change's description:
> Access textures via shared images in RasterDecoderImpl::DoCopySubTextureINTERNAL
> 
> Users only use shared images as input. This allows some validation
> simplification.
> 
> Bug: None
> Change-Id: Ibcfc2229d648743c0c0c859f30157d18348c94ab
> Reviewed-on: https://chromium-review.googlesource.com/c/1415306
> Commit-Queue: Antoine Labour <piman@chromium.org>
> Reviewed-by: Jonathan Backer <backer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#624913}

Change-Id: I7fc0b63b10f656bc4c3ee8b27140f3a8378d392f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: None
Reviewed-on: https://chromium-review.googlesource.com/c/1428381
Cr-Commit-Position: refs/heads/master@{#625018}
9 files changed