only convert in IE9 if the requested responseType is actually an arraybuffer, otherwise just return the responseText. That way the compatibility.js does not break other frameworks like angular that not always want an array from xhr requests.

web/compatibility.js

@@ -171,7 +171,11 @@ if (typeof PDFJS === 'undefined') {
   if (typeof VBArray !== 'undefined') {
     Object.defineProperty(xhrPrototype, 'response', {
       get: function xmlHttpRequestResponseGet() {
+        if (this.responseType === 'arraybuffer') {
           return new Uint8Array(new VBArray(this.responseBody).toArray());
+        } else {
+          return this.responseText;
+        }
       }
     });
     return;