Remove shadow_dom_layout_test.

tests/html/shadow_dom_layout_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 ShadowDOMTest;
-
-import 'dart:html';
-
-// Test that children of a shadow host get distributed properly to the
-// insertion points of a shadow subtree. Output should be three boxes,
-// ordered blue, red, green down the page.
-main() {
-  var div = new DivElement();
-  document.body.children.add(div);
-
-  // build some DOM elements
-  var bluebox = _colorBox('blue', 40, 20);
-  bluebox.classes.add('foo');
-  var redbox = _colorBox('red', 30, 30);
-  var greenbox = _colorBox('green', 60, 10);
-
-  // assemble DOM
-  var sRoot = div.createShadowRoot();
-  sRoot.append(new Element.html('<content select=".foo"></content>'));
-  sRoot.append(redbox);
-  sRoot.append(new Element.tag('content'));
-
-  div.append(bluebox);
-  div.append(greenbox);
-}
-
-DivElement _colorBox(String color, int width, int height) {
-  var style = ('background-color:$color; '
-      'width:${width}px; height:${height}px;');
-  return new Element.html('<div style="$style"></div>');
-}