Added offset document measurement to Element.

tests/html/element_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library ElementTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:async';
 import 'dart:html';
 import 'dart:svg' as svg;
@@ skipping 41 matching lines @@
     test('computedStyle', () {
       final element = document.body;
       var style = element.getComputedStyle();
       expect(style.getPropertyValue('left'), 'auto');
     });
 
     test('client position synchronous', () {
       final container = new Element.tag("div");
       container.style.position = 'absolute';
       container.style.top = '8px';
-      container.style.left = '8px';
+      container.style.left = '9px';
       final element = new Element.tag("div");
       element.style.width = '200px';
       element.style.height = '200px';
       container.children.add(element);
       document.body.children.add(container);
 
       expect(element.client.width, greaterThan(100));
       expect(element.client.height, greaterThan(100));
       expect(element.offset.width, greaterThan(100));
       expect(element.offset.height, greaterThan(100));
       expect(element.scrollWidth, greaterThan(100));
       expect(element.scrollHeight, greaterThan(100));
-      expect(element.getBoundingClientRect().left, 8);
+      expect(element.getBoundingClientRect().left, 9);
       expect(element.getBoundingClientRect().top, 8);
+
+      expect(element.documentOffset.x, 9);
+      expect(element.documentOffset.y, 8);
       container.remove();
     });
   });
 
   group('constructors', () {
     test('error', () {
       expect(() => new Element.html('<br/><br/>'), throwsArgumentError);
     });
 
     test('.html has no parent', () =>
@@ skipping 632 matching lines @@
     });
 
     test('sublist', () {
       var range = makeElList().sublist(1, 3);
       expect(range, isElementList);
       expect(range[0], isImageElement);
       expect(range[1], isInputElement);
     });
   });
 }