Khaki Campbell Duck Release Candidate

[Johann Koenig]

Khaki Campbell has branched from master and is now available on the
'khakicampbell' tag in the libvpx repository.

Please test with your systems and let us know via the bug tracker [0]
or mailing list [1] if you encounter any issues. We hope to finalize
this release in July.

What's new?
- Speed improvements to VP9, especially for low end x86 devices.
- Quality and speed improvements to the VP9 encoder, with special
attention to real-time use.

You can get the code with:
$ git clone https://chromium.googlesource.com/webm/libvpx
$ cd libvpx
$ git checkout khakicampbell

[0] https://bugs.chromium.org/p/webm/issues/list
[1] https://groups.google.com/a/webmproject.org/forum/#!forum/codec-devel