Revert of Re-add suppressions for magnifier and dropshadow GMs. (patchset #1 id:1 of https://codereview.chromium.org/686573002/)

Reason for revert:
Trying to get revert of patchset potentially causing failures on image filter tests

Original issue's description:
> Re-add suppressions for magnifier and dropshadow GMs.
>
> Brian's change has invalidated the new baselines, so they'll need
> to be rebaselined again once his changed has worked its way through.
>
> TBR=bsalomon
> NOTRY=true
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/fa4689d56384da5bb264a480e636fac126fb93ca

TBR=bsalomon@google.com,senorblanco@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/679413002
Revert of Rebaseline imagemagnifier and dropshadowimagefilter tests. (patchset #3 id:40001 of https://codereview.chromium.org/685523002/)

Reason for revert:
Getting to revert for failures on image filter tests in Skia and Blink

Original issue's description:
> Rebaseline imagemagnifier and dropshadowimagefilter tests.
>
> BUG=skia:
> TBR=hcm@google.com
> NOTRY=true
>
> Committed: https://skia.googlesource.com/skia/+/0fc71ea432d3895ede198a24080f877e607cd264

TBR=senorblanco@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/678043003
Revert of Fix bounds computation of all 0-input filters. (patchset #2 id:20001 of https://codereview.chromium.org/681643003/)

Reason for revert:
try again

Original issue's description:
> Fix bounds computation of all 0-input filters.
>
> The SkRectShaderImageFilter had the same bug as previously fixed for
> SkBitmapSource and SkPictureImageFilter. Rather than copy-and-paste
> the implementation, this change makes all filters with 0 inputs return
> their source bounds, instead of returning false.
>
> BUG=427251
>
> Committed: https://skia.googlesource.com/skia/+/ba036cc82b5a543a13cafd11a19ba0e3087fca38

TBR=bsalomon@google.com,senorblanco@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=427251

Review URL: https://codereview.chromium.org/678273002
Revert of Use approximate scratch textures for image filters. (patchset #2 id:20001 of https://codereview.chromium.org/679113004/)

Reason for revert:
Continued GM failures

Original issue's description:
> Use approximate scratch textures for image filters.
>
> Committed: https://skia.googlesource.com/skia/+/96c60686eef6fc514feba6136f1b475f71dbf3ec
>
> Committed: https://skia.googlesource.com/skia/+/50a140563c5960acb2479d2be7c437d146963b3f

TBR=senorblanco@google.com,senorblanco@chromium.org,bsalomon@google.com
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/681183002