First failure in https://uberchromegw.corp.google.com/i/chromeos.chrome/builders/tricky-tot-chrome-pfq-informational/builds/1231/

libchrome-395517-r1: Cloning into '/var/tmp/portage/chromeos-base/libchrome-395517-r1/work/libchrome-395517'...
libchrome-395517-r1: done.
libchrome-395517-r1: fatal: reference is not a tree: 85d6ef31f94c9c39642f0ebc4c1eb08e48edacc1
libchrome-395517-r1:  * ERROR: chromeos-base/libchrome-395517-r1::chromiumos failed (unpack phase):
libchrome-395517-r1:  *   git-2_branch: changing the branch failed
libchrome-395517-r1:  * 
libchrome-395517-r1:  * Call stack:
libchrome-395517-r1:  *     ebuild.sh, line   93:  Called src_unpack
libchrome-395517-r1:  *   environment, line 3332:  Called cros-workon_src_unpack
libchrome-395517-r1:  *   environment, line  826:  Called git-2_src_unpack
libchrome-395517-r1:  *   environment, line 2208:  Called git-2_branch
libchrome-395517-r1:  *   environment, line 1993:  Called die
libchrome-395517-r1:  * The specific snippet of code:
libchrome-395517-r1:  *       git checkout -b ${branchname} ${src} || die "${FUNCNAME}: changing the branch failed";
libchrome-395517-r1:  * 
libchrome-395517-r1:  * If you need support, post the output of `emerge --info '=chromeos-base/libchrome-395517-r1::chromiumos'`,
libchrome-395517-r1:  * the complete build log and the output of `emerge -pqv '=chromeos-base/libchrome-395517-r1::chromiumos'`.
libchrome-395517-r1:  * The complete build log is located at '/var/log/portage/chromeos-base:libchrome-395517-r1:20160623-175029.log'.
libchrome-395517-r1:  * For convenience, a symlink to the build log is located at '/var/tmp/portage/chromeos-base/libchrome-395517-r1/temp/build.log'.
libchrome-395517-r1:  * The ebuild environment file is located at '/var/tmp/portage/chromeos-base/libchrome-395517-r1/temp/environment'.
libchrome-395517-r1:  * Working directory: '/var/tmp/portage/chromeos-base/libchrome-395517-r1/work/libchrome-395517'
libchrome-395517-r1:  * S: '/var/tmp/portage/chromeos-base/libchrome-395517-r1/work/libchrome-395517'
libchrome-395517-r1: >>> Failed to emerge chromeos-base/libchrome-395517-r1, Log file:
libchrome-395517-r1: >>>  '/var/log/portage/chromeos-base:libchrome-395517-r1:20160623-175029.log'