Roll libvpx 228256:232686

Pull latest version from upstream. This had to be broken up across several
changes. The first has the commit message:
https://codereview.chromium.org/55493002/

Remove AVX code until we update the gyp files:
https://codereview.chromium.org/48903015/

libmkv has moved to third_party/libmkv:
https://codereview.chromium.org/54373014/
media/webm/chromeos/webm_encoder.cc and
media/webm/chromeon/ebml_writer.cc pull from this location
as well and needs to be updated.

The last roll attempt failed because we introduced a new textrel.
Fixed upstream and cherry-picked here:
https://codereview.chromium.org/49023003

R=fischman@chromium.org, tomfinegan@chromium.org, fischman, tomfinegan

Review URL: https://codereview.chromium.org/57063005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232721 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232722 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232721
SVN changes up to revision 232722
Mojo: Fixes to get sample to compile

BUG=None
TEST=None
R=darin@chromium.org, darin

Review URL: https://codereview.chromium.org/52483004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232723 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232723