Revert "Revert "Update Closure library to head (5a4878ece3dd35230a21d745411ab0985cf99e15)""

This reverts commit d8a36a4af6010ff5e08760795160f85aa616451a.

Originally reverted because the CI was not using Java 7. That has been fixed,
so this should work now.
Fixing clicks on invisible elements in HtmlUnitDriver broken by ElementNotVisibleException being a subclass of InvalidElementStateException