Accessing a resource through "An Already Defined Origin"

I have a minor set back from the thing that I'm trying to accomplish. Basically : I'm trying to access to a resource in a web service through some other web-site (Since it only allows the access from there)

function loadXMLDoc()
{ 
var xmlhttp;
xmlhttp=new XMLHttpRequest();
xmlhttp.open('GET','http://(Example)',true);
xmlhttp.send();

The code above is what I'm using; I have to reach the resource with GET method. Also, I have to use a Chrome Browser through Android device to successfully reach.

For Android and Chrome problem I'm using User-Agent on Chrome to show myself in both Chrome and Android. But I have to find a way to show myself from the defined origin (Like I've been redirected from there to the resource)

One last thing : I can not edit the defined origin, I have to do it on my own code to show my origin that website.

Thank you guys, Appreciate it.