Polymer/core-ajax — pull request #2 by brendankenny (2014-04-10 00:19:54+00:00)
Title: Add support for arraybuffer and blob responseTypes

to be able to request binary files.

One issue is that these response types and sync xhr are incompatible and will throw an error. However, since sync isn't exposed on core-ajax (only on core-xhr), I assume this isn't a problem.