Revert of Use the upstream version of libwebp, v0.4.3.

Revert of Use the upstream version of libwebp, v0.4.3. (patchset #6 id:70001 of https://codereview.chromium.org/1178013008/)

Reason for revert:
Breaking the build e.g. http://build.chromium.org/p/client.skia/builders/Perf-Mac10.8-Clang-MacMini4.1-GPU-GeForce320M-x86_64-Release/builds/1082/steps/build%20nanobench/logs/stdio

../../../third_party/externals/libwebp/src/utils/./endian_inl.h:51:10: error: use of unknown builtin '__builtin_bswap16' [-Wimplicit-function-declaration]
  return __builtin_bswap16(x);
         ^
1 error generated.

Original issue's description:
> Use the upstream version of libwebp, v0.4.3.
> 
> DEPS:
> Update to pull v0.4.3 of libwebp from upstream
> 
> gyp/libwebp.gyp:
> Add new files, as referenced by the gyp file used by Chromium.
> 
> resource/tests:
> Add regression tests for particular images.
> 
> BUG=skia:3442
> BUG=skia:3315
> BUG=skia:3429
> 
> Committed: https://skia.googlesource.com/skia/+/3aa0fb4d80c76b559ff4b82d5e569993aea06da1

TBR=djsollen@google.com,jzern@chromium.org,msarett@google.com,emmaleer@google.com,scroggo@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:3442
Committed: https://skia.googlesource.com/skia/+/c1d1dd738e8dda1dd439f8e2b065ec73b5c12b51

[scroggo, 2015-07-08 17:57:05]

Created Revert of Use the upstream version of libwebp, v0.4.3.

[commit-bot: I haz the power, 2015-07-08 17:57:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1223583004/1

[commit-bot: I haz the power, 2015-07-08 17:57:27]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/c1d1dd738e8dda1dd439f8e2b065ec73b5c12b51