Move apiUtils.js to ES6.

Review Request #8045 — Created March 9, 2016 and submitted — Latest diff uploaded

Information

Review Board
release-2.6.x
6f45d4d...

Reviewers

This change renames the file and does a bunch of cleanup. ES6 lets us use nice
things like let/const and arrow functions, and some of this is just
long-overdue cleanup to bring things into a modern style.

Ran js-tests.