Moving ListBase, FixedLengthListMixin and UmodifiableListMixin to collection.

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 18604bc4b9c67123bb70024626092775b804aa1c..bf77120d8273d079d1e0033e9289e5ba156ad93e 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -8870,7 +8870,7 @@ class DomTokenList extends NativeFieldWrapperClass1 {
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
-class _ChildrenElementList implements List {
+class _ChildrenElementList implements List<Element> {
   // Raw Element.
   final Element _element;
   final HtmlCollection _childElements;
@@ -8928,19 +8928,19 @@ class _ChildrenElementList implements List {
   }
 
   String join([String separator]) {
-    return IterableMixinWorkaround.joinList(this, separator);
+    return _childElements.join(separator);
   }
 
   Iterable map(f(Element element)) {
-    return IterableMixinWorkaround.mapList(this, f);
+    return _childElements.map(f);
   }
 
   Iterable<Element> where(bool f(Element element)) {
-    return IterableMixinWorkaround.where(this, f);
+    return _childElements.where(f);
   }
 
   Iterable expand(Iterable f(Element element)) {
-    return IterableMixinWorkaround.expand(this, f);
+    return _childElements.expand(f);
   }
 
   bool get isEmpty {
@@ -33352,7 +33352,7 @@ class _WrappedList<E> implements List<E> {
     _list.insertRange(start, length, fill);
   }
 
-  Map<int, E> asMap() => IterableMixinWorkaround.asMapList(_list);
+  Map<int, E> asMap() => _list.asMap();
 
   String toString() {
     StringBuffer buffer = new StringBuffer('[');