Prevent default actions for JS-generated mouse events other than click

LayoutTests/fast/forms/range/slider-zoomed.html

Index: LayoutTests/fast/forms/range/slider-zoomed.html
diff --git a/LayoutTests/fast/forms/range/slider-zoomed.html b/LayoutTests/fast/forms/range/slider-zoomed.html
index 23a36814cd7bcda4929ba939ba9a9a0b5ed99714..fc92ec4571376a2a8ac57dc98b0d25d6cb85578a 100644
--- a/LayoutTests/fast/forms/range/slider-zoomed.html
+++ b/LayoutTests/fast/forms/range/slider-zoomed.html
@@ -17,20 +17,13 @@
   <script type="text/javascript" charset="utf-8">
     if (window.testRunner)
         testRunner.dumpAsText();
-
-    function dispatchEvent(eventType, clientX, clientY)
-    {
-      var ev = document.createEvent("MouseEvent");
-      ev.initMouseEvent(eventType, true, true, window, 1, 1, 1, clientX, clientY, false, false, false, false, 0, document);
-      var target = document.elementFromPoint(ev.clientX, ev.clientY);
-      target.dispatchEvent(ev);
-    }
     
     function test()
     {
       // For some reason the slider needs mouseup/mousedown, not just a "click"
-      dispatchEvent("mousedown", 150, 15);
-      dispatchEvent("mouseup", 150, 15);
+      eventSender.mouseMoveTo(150, 15);
+      eventSender.mouseDown(0);
+      eventSender.mouseUp(0);
 
       const expectedValue = 72;
       var val = document.getElementById('slider').value;