Promote DOMType to public dart:dom type.

client/dom/common/implementation.dart

-class DOMType extends DOMWrapperBase {
-  // FIXME: Remove if/when Dart supports OLS for all objects.
-  var dartObjectLocalStorage;
-
-  String get typeName() {
-    throw new UnsupportedOperationException("typeName must be overridden.");
-  }
-}
-
 class ListBase<E> extends DOMType implements List<E> {
   ListBase();
 
   void forEach(void f(E element)) => Collections.forEach(this, f);
   Collection<E> filter(bool f(E element)) => Collections.filter(this, [], f);
   bool every(bool f(E element)) => Collections.every(this, f);
   bool some(bool f(E element)) => Collections.some(this, f);
   bool isEmpty() => Collections.isEmpty(this);
 
   void sort(int compare(E a, E b)) {
@@ skipping 102 matching lines @@
   }
 
   V remove(K key) {
     throw 'Immutable collection';
   }
 
   Collection<K> getKeys() {
     throw 'Must be implemented';
   }
 }