I'm not quite familiar with running Ripple as an extension, but in a stand-alone setup this call (for good or for bad) is used to "cordoba prepare" the project for the platform being emulated. I'm wondering why it's failing in the extension. Perhaps, it's the right time for me to set it up and try...

On Mon, May 18, 2015 at 7:49 AM, Shubham Kesarwani <shubhamkesar@icloud.com> wrote:
The User Agent setup call (in lib/client/index.js) is commented to be somewhat ‘To-Be-Moved’. This makes a failed attempt at XHR POST request which is visible in the web console.

Removing this call for the chrome extension seems like a better idea than for someone to end up looking for what got wrong during the run. (Me)

Line 132 is the culprit in the same source file index.js also seen below in the image.