State transition breaks ES6 Map when passed through optional $stateParams in a ui-sref

[mrohr]

When using an ES6 Map as a optional state param in order to pass data from one state to another, the Map object's methods stop working once passed through to another state.

http://plnkr.co/edit/TVANV1Cnb8B7h95mNjmW?p=preview

in the plunkr, transitioning between states without passing any stateParams works, and just instantiates a new Map. If you click one of the links that passes the Map as a stateParam, the plunkr breaks with the error:

Method Map.prototype.<methodName> called on incompatible receiver #<Map>

[mrohr]

Just did a little more digging, and its specifically ui-sref links with params that break. I've updated the plunkr to add two buttons that call $state.go instead, and those pass the parameters as expected.

http://plnkr.co/edit/b5Sja92rOcMpeKUrgebL?p=preview