Added offset document measurement to Element.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index f817506bd27c1a42ca959f8c97d8cc07ecb9531c..461865bcd2c6ced0ee8ec6be58939c28917b1d5d 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -9161,6 +9161,43 @@ abstract class Element extends Node implements ElementTraversal {
    */
   @Experimental()
   CssRect get marginEdge => new _MarginCssRect(this);
+
+  /** 
+   * Provides the coordinates of the element relative to the top of the 
+   * document. 
+   *
+   * This method is the Dart equivalent to jQuery's 
+   * [offset](http://api.jquery.com/offset/) method.
+   */
+  Point get docOffset => offsetTo(document.documentElement);
+
+  /** 
+   * Provides the offset of this element's [borderEdge] relative to the
+   * specified [parent].
+   * 
+   * This is the Dart equivalent of jQuery's
+   * [position](http://api.jquery.com/position/) method. Unlike jQuery's
+   * position, however, [parent] can be any parent element of `this`, 
+   * rather than only `this`'s immediate offsetParent. If the specified element
+   * is _not_ an offset parent or transitive offset parent to this element,
+   * an ArgumentError is thrown.
+   */
+  Point offsetTo(Element parent) {
+    return _offsetToHelper(this, 
+        parent, parent == this || parent.tagName == 'HTML');
+  }
+
+  Point _offsetToHelper(Element current, Element parent, bool foundAsParent) {
+    if (current == null || current == parent) {
+      return foundAsParent? new Point(0, 0) : throw new ArgumentError(
+          "Specified element is not a transitive offset parent of this "
+          "element.");
+    } 
+    Element parentOffset = current.offsetParent;
+    Point p = _offsetToHelper(
+        parentOffset, parent, foundAsParent || parentOffset == parent);
+    return new Point(p.x + current.offsetLeft, p.y + current.offsetTop);
+  }
   // To suppress missing implicit constructor warnings.
   factory Element._() { throw new UnsupportedError("Not supported"); }