When sync is set to true, iron-ajax ignores handle-as attribute.

[jasonmlkang]

Description

When sync is set to true, iron-ajax ignores handle-as attribute.

Steps to reproduce

1.sync="true" 2. handle-as="json"

[stramel]

Hmmm looks like maybe the code got shifted around accidentally?

https://github.com/PolymerElements/iron-ajax/blob/master/iron-request.html#L249

https://github.com/PolymerElements/iron-ajax/blob/master/iron-request.html#L281

Looks like it is also affecting jsonPrefix