ChildPortHandshake is the most generic system yet to allow child
processes to provide their parents with Mach rights. These are
ordinarily expected to be send rights to the children’s own task ports,
or send rights to servers that the children hold receive rights to.
This updates DEPS to pull mini_chromium 1d3523dbda93, which includes
base::mac::ScopedMachPortSet.
TEST=util_test ChildPortHandshake.*
R=rsesek@chromium.org
Review URL: https://codereview.chromium.org/756603003