Reland "Remove WheelEvent.initWebKitWheelEvent()"

LayoutTests/fast/events/wheelevent-in-scrolling-div.html

Index: LayoutTests/fast/events/wheelevent-in-scrolling-div.html
diff --git a/LayoutTests/fast/events/wheelevent-in-scrolling-div.html b/LayoutTests/fast/events/wheelevent-in-scrolling-div.html
index dbd8dc2e57d4af049e7360395192ff664a56d49b..e0cacc3e4b08f4a34f2d6fae9ab5cb0a75dfad27 100644
--- a/LayoutTests/fast/events/wheelevent-in-scrolling-div.html
+++ b/LayoutTests/fast/events/wheelevent-in-scrolling-div.html
@@ -16,9 +16,16 @@
                 if (overflowElement) {
                     overflowElement.addEventListener("mousewheel", mousewheelHandler, false);
 
-                    var wheelEvent = document.createEvent("WheelEvent");
-                    wheelEvent.initWebKitWheelEvent(-window.expectedScrollLeft, -window.expectedScrollTop, window, 0, 0, 0, 0, false, false, false, false);
-                    overflowElement.dispatchEvent(wheelEvent);
+                    var deltaX = window.expectedScrollLeft;
+                    var deltaY = window.expectedScrollTop;
+                    var eventInit = {
+                        deltaX: deltaX,
+                        deltaY: deltaY,
+                        wheelDeltaX: -120 * deltaX,
+                        wheelDeltaY: -120 * deltaY,
+                    };
+                    var event = new WheelEvent("mousewheel", eventInit);
+                    overflowElement.dispatchEvent(event);
                 }
 
                 setTimeout('checkOffsets();', 100);
@@ -37,6 +44,8 @@
             function mousewheelHandler(e)
             {
                 event = e;
+                shouldBe("event.deltaY", "window.expectedScrollTop");
+                shouldBe("event.deltaX", "window.expectedScrollLeft");
                 shouldBe("event.wheelDeltaY", "window.expectedScrollTop*-120");
                 shouldBe("event.wheelDeltaX", "window.expectedScrollLeft*-120");