Update CAS login to return url rather than update location as the JS SDK may not be run within a browser env

lib/client.js

@@ -1722,12 +1722,14 @@ MatrixClient.prototype.loginWithSAML2 = function(relayState, callback) {
 };
 
 /**
- * @param {string} redirectUrl URL to which to be redirect to after
+ * @param {string} redirectUrl URL to which to be redirected to after
  * HS authenticates with CAS and issues login token
- * Will redirect to homeserver to complete CAS login
+ * @return {string} CAS login URL
  */
-MatrixClient.prototype.loginWithCas = function(redirectUrl) {
+MatrixClient.prototype.getCasLoginUrl = function(redirectUrl) {
-    this._http.redirect("/login/cas/redirect", {"redirectUrl": redirectUrl}, httpApi.PREFIX_V1);
+    return this._http.getUrl("/login/cas/redirect", {
+        "redirectUrl": redirectUrl
+    }, httpApi.PREFIX_V1);
 };
 
 /**

lib/http-api.js

@@ -296,13 +296,23 @@ module.exports.MatrixHttpApi.prototype = {
         return this._request(callback, method, fullUri, queryParams, data);
     },
 
-    redirect: function(path, queryParams, prefix) {
+    /**
+     * Form and return a homeserver request URL based on the given path
+     * params and prefix.
+     * @param {string} path The HTTP path <b>after</b> the supplied prefix e.g.
+     * "/createRoom".
+     * @param {Object} queryParams A dict of query params (these will NOT be
+     * urlencoded).
+     * @param {string} prefix The full prefix to use e.g.
+     * "/_matrix/client/v2_alpha".
+     * @return {string} URL
+     */
+    getUrl: function(path, queryParams, prefix) {
         var queryString = "";
         if (queryParams) {
             queryString = "?" + utils.encodeParams(queryParams);
         }
-        var fullUri = this.opts.baseUrl + prefix + path + queryString;
+        return this.opts.baseUrl + prefix + path + queryString;
-        window.location.href = fullUri;
     },
 
     _request: function(callback, method, uri, queryParams, data) {