[milo] do not use EcmaScript6 in time.js
[milo] do not use EcmaScript6 in time.js

We cannot use ES6 in console view.

Bug: 791528
Change-Id: I3df6440e685418ce81db04591c491b2993a7f381
Reviewed-on: https://chromium-review.googlesource.com/806874
Reviewed-by: Erik Staab <9e0728822fdb2ce07b011b42510312bb837e6a51@chromium.org>
Reviewed-by: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>
Commit-Queue: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go