Revert of Update feSpotLight to match spec

Revert of Update feSpotLight to match spec (patchset #2 id:20001 of https://codereview.chromium.org/1403403003/ )

Reason for revert:
re-land once layout test have been disabled (so they can be rebased)

Original issue's description:
> Update feSpotLight to match spec
> 
> This change updates feSpotLight to match the spec via two changes:
> 
> 1) specularExponent is ignored if the spotlight has no coneAngle (GPU
>    bug only). This change updates the GPU path so that it matches the
>    CPU path and the spec in this regard.
> 
> 2) specularExponent is clamped to the 1-128 range. The spec does not
>    specify a clamp for the specularExponent attribute of feSpotLight.
>    Note that the spec *does* specify this clamp for the
>    specularExponent attribute of feSpecularLighting. It looks like we
>    incorrectly applied this to both specularExponent attributes.
> 
>    This change (along with a parallel change in Blink) allows us to pass
>    the SVG filter effects conformance test here:
>    http://www.w3.org/Graphics/SVG/Test/20110816/harness/htmlObject/filters-light-01-f.html
> 
>    Additionally, this brings our behavior in line with Safari and Edge’s
>    behavior on this filter.
> 
> Two new cases were added to gm/lighting.cpp to catch these issues:
> - The existing spotlight case exercised the path where our specular
>   exponent was between 1-128 and had a limiting cone angle.
> - The first new spotlight case exercises the path where our specular
>   exponent is between 1-128 and we do not have a limiting cone angle.
> - The second new spotlight case exercises the path where the specular
>   exponent is not within the 1-128 range, to ensure that we don’t
>   incorrectly clip to this range.
> 
> BUG=472849
> 
> Committed: https://skia.googlesource.com/skia/+/c84ccb070258db2803a9e8f532bfe7239a737063

TBR=senorblanco@google.com,senorblanco@chromium.org,bsalomon@google.com,ericrk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=472849
Committed: https://skia.googlesource.com/skia/+/0bccd8749bdce79b2d71518fe65783b1a9b06445

[caryclark, 2015-10-20 17:03:47]

Created Revert of Update feSpotLight to match spec

[commit-bot: I haz the power, 2015-10-20 17:03:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1417463006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1417463006/1

[commit-bot: I haz the power, 2015-10-20 17:04:05]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/0bccd8749bdce79b2d71518fe65783b1a9b06445