CSSStyleDeclaration.getPropertyValue returns empty string instead of null.

lib/html/dart2js/html_dart2js.dart

Index: lib/html/dart2js/html_dart2js.dart
===================================================================
--- lib/html/dart2js/html_dart2js.dart	(revision 13188)
+++ lib/html/dart2js/html_dart2js.dart	(working copy)
@@ -4228,8 +4228,6 @@
 
   String getPropertyShorthand(String propertyName) native;
 
-  String getPropertyValue(String propertyName) native;
-
   bool isPropertyImplicit(String propertyName) native;
 
   String item(int index) native;
@@ -4237,6 +4235,15 @@
   String removeProperty(String propertyName) native;
 
 
+  String getPropertyValue(String propertyName) {
+    var propValue = JS('Object', '#.getPropertyValue(#)', this, propertyName);
+    if (propValue == null) {
+      return '';
+    } else {
+      return propValue;
+    }
+  }
+
   void setProperty(String propertyName, String value, [String priority]) native '''
     this.setProperty(propertyName, value, priority);
     // Bug #2772, IE9 requires a poke to actually apply the value.
@@ -22342,15 +22349,96 @@
 // WARNING: Do not edit - generated code.
 
 /// @domName RadioNodeList
-abstract class RadioNodeList implements List<Node> {
+abstract class RadioNodeList implements List<Node>, List<Node> {
 
   /** @domName RadioNodeList.value */
   String value;
 }
 
-class _RadioNodeListImpl extends _NodeListImpl implements RadioNodeList native "*RadioNodeList" {
+class _RadioNodeListImpl extends _NodeListImpl implements RadioNodeList, JavaScriptIndexingBehavior native "*RadioNodeList" {
 
   String value;
+
+  _NodeImpl operator[](int index) native "return this[index];";
+
+  void operator[]=(int index, _NodeImpl value) {
+    throw new UnsupportedOperationException("Cannot assign element of immutable List.");
+  }
+  // -- start List<Node> mixins.
+  // Node is the element type.
+
+  // From Iterable<Node>:
+
+  Iterator<Node> iterator() {
+    // Note: NodeLists are not fixed size. And most probably length shouldn't
+    // be cached in both iterator _and_ forEach method. For now caching it
+    // for consistency.
+    return new _FixedSizeListIterator<Node>(this);
+  }
+
+  // From Collection<Node>:
+
+  void add(Node value) {
+    throw const UnsupportedOperationException("Cannot add to immutable List.");
+  }
+
+  void addLast(Node value) {
+    throw const UnsupportedOperationException("Cannot add to immutable List.");
+  }
+
+  void addAll(Collection<Node> collection) {
+    throw const UnsupportedOperationException("Cannot add to immutable List.");
+  }
+
+  void forEach(void f(Node element)) => _Collections.forEach(this, f);
+
+  Collection map(f(Node element)) => _Collections.map(this, [], f);
+
+  Collection<Node> filter(bool f(Node element)) =>
+     _Collections.filter(this, <Node>[], f);
+
+  bool every(bool f(Node element)) => _Collections.every(this, f);
+
+  bool some(bool f(Node element)) => _Collections.some(this, f);
+
+  bool isEmpty() => this.length == 0;
+
+  // From List<Node>:
+
+  void sort(int compare(Node a, Node b)) {
+    throw const UnsupportedOperationException("Cannot sort immutable List.");
+  }
+
+  int indexOf(Node element, [int start = 0]) =>
+      _Lists.indexOf(this, element, start, this.length);
+
+  int lastIndexOf(Node element, [int start]) {
+    if (start === null) start = length - 1;
+    return _Lists.lastIndexOf(this, element, start);
+  }
+
+  Node last() => this[length - 1];
+
+  Node removeLast() {
+    throw const UnsupportedOperationException("Cannot removeLast on immutable List.");
+  }
+
+  void setRange(int start, int rangeLength, List<Node> from, [int startFrom]) {
+    throw const UnsupportedOperationException("Cannot setRange on immutable List.");
+  }
+
+  void removeRange(int start, int rangeLength) {
+    throw const UnsupportedOperationException("Cannot removeRange on immutable List.");
+  }
+
+  void insertRange(int start, int rangeLength, [Node initialValue]) {
+    throw const UnsupportedOperationException("Cannot insertRange on immutable List.");
+  }
+
+  List<Node> getRange(int start, int rangeLength) =>
+      _Lists.getRange(this, start, rangeLength, <Node>[]);
+
+  // -- end List<Node> mixins.
 }
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a