Release Notes:
- https://www.gerritcodereview.com/2.15.html#21515
- https://www.gerritcodereview.com/2.15.html#21516
- https://www.gerritcodereview.com/2.15.html#21517
Main things we want:
We want the new extension point for the footer. This will allow us to further prepare for Polymer 2.