Revert revision 16240

samples/swarm/swarm_ui_lib/touch/FxUtil.dart

Index: samples/swarm/swarm_ui_lib/touch/FxUtil.dart
===================================================================
--- samples/swarm/swarm_ui_lib/touch/FxUtil.dart	(revision 16245)
+++ samples/swarm/swarm_ui_lib/touch/FxUtil.dart	(working copy)
@@ -67,24 +67,14 @@
    * changed.
    */
   static Coordinate computeRelativePosition(Element element, Element target) {
-    final elementPoint = computePagePosition(element);
-    final targetPoint = computePagePosition(target);
-    return new Coordinate(elementPoint.x - targetPoint.x,
-        elementPoint.y - targetPoint.y);
+    final testPoint = new Point(0, 0);
+    final pagePoint =
+        window.webkitConvertPointFromNodeToPage(element, testPoint);
+    final pointRelativeToTarget =
+        window.webkitConvertPointFromPageToNode(target, pagePoint);
+    return new Coordinate(pointRelativeToTarget.x, pointRelativeToTarget.y);
   }
 
-  /** Computes the position of an element on the page. */
-  static Coordinate computePagePosition(Element element) {
-    num left = 0;
-    num top = 0;
-    do {
-      left += element.offsetLeft;
-      top += element.offsetTop;
-      element = element.offsetParent;
-    } while (element != null);
-    return new Coordinate(left, top);
-  }
-
   /** Clear a -webkit-transform from an element. */
   static void clearWebkitTransform(Element el) {
     el.style.transform = '';