hashchange event is inconsistent on IE11

[robrez]

Description

iron-location's handling of history api seems to be causing IE11 to not fire hashchange events in some edge-case scenarios. I'm able to reproduce whenever the site uses anchor tags for some navigation and javascript for some other navigation.

Expected outcome

browser fires hashchange event

Actual outcome

browser doesn't fire hashchange event

Live Demo

http://codepen.io/robrez/pen/zKNGmK

Steps to reproduce

The issue seems to occur iff you navigate using an anchor, then navigate using javascript, then navigate using the anchor that was previously used. In otherwords, given two routes A and B, if you navigate like this: A->B->A->B and A uses an anchor, but B uses javascript, hashchange events cease to fire.

If A and B both use anchors or A and B both use javascript, the issue does not seem to occur.

In the live demo provided, you can see the breakdown by clicking bravo->charlie->bravo->charlie
Note that iron-location incorrectly reports a hash of "bravo". Proceeding to a different route, eg delta, "fixes" the problem

I only speculate that this relates to iron-location because I have a separate demo that doesn't use iron-location. In that demo, hashchange events continue firing in every situation I've tested

Browsers Affected

• Chrome
• Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10