Revert of Update libwebp and resume testing scaled webp

Revert of Update libwebp and resume testing scaled webp (patchset #2 id:20001 of https://codereview.chromium.org/1280073002/ )

Reason for revert:
Compile failures, e.g.

http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-Arm7-Debug-Android_NoNeon/builds/1427/steps/build%20most/logs/stdio

Original issue's description:
> Update libwebp and resume testing scaled webp
> 
> libwebp has a fix for [1]. Update to the commit that contains the fix.
> 
> Update libwebp.gypi, corresponding to libwebp's latest makefile.
> 
> Turn back on DM testing for scaled webp, now that it should no longer
> use uninitialized memory.
> 
> Fix a warning in config.h
> 
> [1] https://code.google.com/p/webp/issues/detail?id=254
> 
> BUG=skia:4038
> 
> Committed: https://skia.googlesource.com/skia/+/0575d3e6c272744a66ab3281f9871366717df339

TBR=djsollen@google.com,msarett@google.com,scroggo@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:4038
Committed: https://skia.googlesource.com/skia/+/0df0e43488dc785815d3234d9bd60bad91532f98

[scroggo, 2015-08-07 19:53:08]

Created Revert of Update libwebp and resume testing scaled webp

[commit-bot: I haz the power, 2015-08-07 19:53:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1278173004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1278173004/1

[commit-bot: I haz the power, 2015-08-07 19:53:28]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/0df0e43488dc785815d3234d9bd60bad91532f98