Add tests for Element#elements.

client/html/src/NodeWrappingImplementation.dart

Index: client/html/src/NodeWrappingImplementation.dart
diff --git a/client/html/src/NodeWrappingImplementation.dart b/client/html/src/NodeWrappingImplementation.dart
index 5a89e5e8c4e28ae87415e4d7d679b510a5ae198c..82a568c3d597bc38a7caf612d662bf6e0edf7981 100644
--- a/client/html/src/NodeWrappingImplementation.dart
+++ b/client/html/src/NodeWrappingImplementation.dart
@@ -25,23 +25,9 @@ class _ChildrenNodeList implements NodeList {
 
   void forEach(void f(Node element)) => _toList().forEach(f);
 
-  Collection map(f(Node element)) {
-    List output = new List();
-    forEach((Node element) {
-        output.add(f(element));
-    });
-    return output;
-  }
+  Collection map(f(Node element)) => _toList().map(f);
 
-  Collection<Node> filter(bool f(Node element)) {
-    List<Node> output = new List<Node>();
-    forEach((Node element) {
-      if (f(element)) {
-        output.add(element);
-      }
-    });
-    return output;
-  }
+  Collection<Node> filter(bool f(Node element)) => _toList().filter(f);
 
   bool every(bool f(Node element)) {
     for(Node element in this) {
@@ -111,71 +97,25 @@ class _ChildrenNodeList implements NodeList {
     throw 'Not impl yet. todo(jacobr)';
   }
 
-  void setRange(int start, int length, List from, [int startFrom = 0]) {
-    // TODO(nweiz): remove these IndexOutOfRange checks once Frog has bounds
-    // checking for List indexing
-    if (start < 0) {
-      throw new IndexOutOfRangeException(start);
-    } else if (startFrom < 0) {
-      throw new IndexOutOfRangeException(startFrom);
-    } else if (length < 0) {
-      throw new IllegalArgumentException("negative length $length");
-    } else if (start + length > this.length) {
-      throw new IndexOutOfRangeException(Math.min(this.length, start));
-    } else if (startFrom + length > from.length) {
-      throw new IndexOutOfRangeException(Math.min(from.length, startFrom));
-    }
-
-    for (var i = 0; i < length; i++) {
-      this[start + i] = from[startFrom + i];
-    }
-  }
-
-  void removeRange(int start, int length) {
-    // TODO(nweiz): remove these IndexOutOfRange checks once Frog has bounds
-    // checking for List indexing
-    if (start < 0) {
-      throw new IndexOutOfRangeException(start);
-    } else if (length < 0) {
-      throw new IllegalArgumentException("negative length $length");
-    } else if (start + length > this.length) {
-      throw new IndexOutOfRangeException(Math.min(this.length, start));
-    }
+  void setRange(int start, int length, List from, [int startFrom = 0]) =>
+    Lists.setRange(this, start, length, from, startFrom);
 
-    for (var i = 0; i < length; i++) {
-      this[start].remove();
-    }
-  }
+  void removeRange(int start, int length) =>
+    Lists.removeRange(this, start, length, (i) => this[i].remove());
 
   void insertRange(int start, int length, [initialValue = null]) {
     throw const NotImplementedException();
   }
 
-  List getRange(int start, int length) {
-    // TODO(nweiz): remove these IndexOutOfRange checks once Frog has bounds
-    // checking for List indexing
-    if (start < 0) {
-      throw new IndexOutOfRangeException(start);
-    } else if (length < 0) {
-      throw new IllegalArgumentException("negative length $length");
-    } else if (start + length > this.length) {
-      throw new IndexOutOfRangeException(Math.min(this.length, start));
-    }
-
-    var nodes = <Node>[];
-    for (var i = 0; i < length; i++) {
-      nodes.add(this[start + i]);
-    }
-    return nodes;
-  }
+  List getRange(int start, int length) => Lists.getRange(this, start, length);
 
   int indexOf(Node element, [int start = 0]) {
-    return _Lists.indexOf(this, element, start, this.length);
+    return Lists.indexOf(this, element, start, this.length);
   }
 
   int lastIndexOf(Node element, [int start = null]) {
     if (start === null) start = length - 1;
-    return _Lists.lastIndexOf(this, element, start);
+    return Lists.lastIndexOf(this, element, start);
   }
 
   void clear() {