Revert of Rebaseline imagemagnifier and dropshadowimagefilter tests. (patchset #3...

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