Roll libvpx 255744:255831

BUG=350540

Review URL: https://codereview.chromium.org/191003008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255843 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255844 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255844