getChatterFile should use the proxyUrl if it is set, required by Visualforce apps

Author: vnehess

forcetk.js

@@ -199,13 +199,16 @@ if (forcetk.Client === undefined) {
         var url = this.instanceUrl + path;
 
         var request = new XMLHttpRequest();
-        
-                
-        request.open("GET", url, true);
+
+                       
+        request.open("GET",  (this.proxyUrl !== null) ? this.proxyUrl: url, true);
         request.responseType = "arraybuffer";
 
         request.setRequestHeader(that.authzHeader, "OAuth " + that.sessionId);
         request.setRequestHeader('X-User-Agent', 'salesforce-toolkit-rest-javascript/' + that.apiVersion);
+        if (that.proxyUrl !== null) {
+            request.setRequestHeader('SalesforceProxy-Endpoint', url);
+        }
 
         request.onreadystatechange = function() {
             // continue if the process is completed