add 'opts' argument to mouseEvent asset

Author: etpinard

test/jasmine/assets/mouse_event.js

@@ -1,11 +1,16 @@
-module.exports = function(type, x, y) {
-    var options = {
+module.exports = function(type, x, y, opts) {
+    var fullOpts = {
         bubbles: true,
         clientX: x,
         clientY: y
     };
 
+    // https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent
+    if(opts) {
+        if(opts.buttons) fullOpts.buttons = opts.buttons;
+    }
+
     var el = document.elementFromPoint(x,y);
-    var ev = new window.MouseEvent(type, options);
+    var ev = new window.MouseEvent(type, fullOpts);
     el.dispatchEvent(ev);
 };