Revert of Add helper to validate JPEG decode subsampling factors

Revert of Add helper to validate JPEG decode subsampling factors (patchset #1 id:1 of https://codereview.chromium.org/1039503003/)

Reason for revert:
Per the bug, Factor 3 images are acceptable to libjpeg6b and users can even create them using its well-known cjpeg tool. 

Original issue's description:
> Add helper to validate JPEG subsampling factors
> 
> Use it to turn the invalid horizontal/vertical subsampling factor 3 to a
> 1, which is fine for both the YUV decoding path (it won't turn on if any 
> of the component subsamplings is 3) and the normal JPEG decode path.
> 
> TEST=Covered by the test added in r192900
> BUG=398235
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192980

TBR=sugoi@chromium.org,reveman@chromium.org,pdr@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=398235
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=193326

[Noel Gordon, 2015-04-08 05:12:36]

Created Revert of Add helper to validate JPEG decode subsampling factors

[commit-bot: I haz the power, 2015-04-08 05:12:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1069083003/1

[commit-bot: I haz the power, 2015-04-08 05:13:36]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=193326