Reapply removeWhere and retainWhere for elements in dart:html

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
 import 'dart:json' as json;
@@ skipping 7233 matching lines @@
 
     for (Element element in iterable) {
       _element.append(element);
     }
   }
 
   void sort([int compare(Element a, Element b)]) {
     throw new UnsupportedError('Cannot sort element lists');
   }
 
+  void removeWhere(bool test(Element element)) {
+    _filter(test, false);
+  }
+
+  void retainWhere(bool test(Element element)) {
+    _filter(test, true);
+  }
+
+  void _filter(bool test(var element), bool retainMatching) {
+    Iterable removed = [];
+    if (retainMatching) {
+      removed = _element.children.where((e) => !test(e));
+    } else {
+      removed = _element.children.where(test);
+    }
+    for (var e in removed) e.remove();
+  }
+
   void setRange(int start, int end, Iterable<Element> iterable,
                 [int skipCount = 0]) {
     throw new UnimplementedError();
   }
 
   void replaceRange(int start, int end, Iterable<Element> iterable) {
     throw new UnimplementedError();
   }
 
   void fillRange(int start, int end, [Element fillValue]) {
@@ skipping 22034 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }