feat #283: improve error message on timeout on browser platform

src/browser/cordova-http-plugin.js

@@ -171,10 +171,19 @@ function sendRequest(method, withData, opts, success, failure) {
   xhr.responseType = responseType;
   setHeaders(xhr, headers);
 
-  xhr.onerror = xhr.ontimeout = function () {
+  xhr.onerror = function () {
     return failure(createXhrFailureObject(xhr));
   };
 
+  xhr.ontimeout = function () { 
+    return failure({
+      status: -4,
+      error: 'Request timed out',
+      url: url,
+      headers: {}
+    });
+  };
+
   xhr.onload = function () {
     if (xhr.readyState !== xhr.DONE) return;