Reland "Remove WheelEvent.initWebKitWheelEvent()"

LayoutTests/fast/forms/resources/common-wheel-event.js

 function dispatchWheelEvent(element, deltaX, deltaY)
 {
-    var event = document.createEvent('WheelEvent');
-    var dontCare = 0;
-    event.initWebKitWheelEvent(deltaX, deltaY, document.defaultView, dontCare, dontCare, dontCare, dontCare, false, false, false, false);
+    var eventInit = { deltaX: -deltaX, deltaY: -deltaY };
+    var event = new WheelEvent('mousewheel', eventInit);
     element.dispatchEvent(event);
 }
 
 var input;
 function testWheelEvent(parameters)
 {
     var inputType = parameters['inputType'];
     var initialValue = parameters['initialValue'];
     var stepUpValue1 = parameters['stepUpValue1'];
     var stepUpValue2 = parameters['stepUpValue2'];
@@ skipping 33 matching lines @@
     shouldBeEqualToString('input.value', initialValue);
     input.readOnly = false;
 
     debug('No focus:');
     document.getElementById('another').focus();
     dispatchWheelEvent(input, 0, 1);
     shouldBeEqualToString('input.value', initialValue);
 
     parent.parentNode.removeChild(parent);
 }