Add tests for Element#elements.

client/html/src/ElementWrappingImplementation.dart

Index: client/html/src/ElementWrappingImplementation.dart
diff --git a/client/html/src/ElementWrappingImplementation.dart b/client/html/src/ElementWrappingImplementation.dart
index 38b82dff028c94a10426cd2c1c21c7c9095387d1..a10b510fb39e63c0527ff1aa4a16d585c90a7799 100644
--- a/client/html/src/ElementWrappingImplementation.dart
+++ b/client/html/src/ElementWrappingImplementation.dart
@@ -24,29 +24,11 @@ class _ChildrenElementList implements ElementList {
     return LevelDom.wrapElement(_element.firstElementChild);
   }
 
-  void forEach(void f(Element element)) {
-    for (var element in _childElements) {
-      f(LevelDom.wrapElement(element));
-    }
-  }
+  void forEach(void f(Element element)) => _toList().forEach(f);
 
-  Collection map(f(Element element)) {
-    List output = new List();
-    forEach((Element element) {
-      output.add(f(element));
-    });
-    return output;
-  }
+  Collection map(f(Element element)) => _toList().map(f);
 
-  Collection<Element> filter(bool f(Element element)) {
-    List<Element> output = new List<Element>();
-    forEach((Element element) {
-      if (f(element)) {
-        output.add(element);
-      }
-    });
-    return output;
-  }
+  Collection<Element> filter(bool f(Element element)) => _toList().filter(f);
 
   bool every(bool f(Element element)) {
     for(Element element in this) {
@@ -67,7 +49,7 @@ class _ChildrenElementList implements ElementList {
   }
 
   bool isEmpty() {
-    return _element.firstElementChild !== null;
+    return _element.firstElementChild === null;
   }
 
   int get length() {
@@ -110,29 +92,25 @@ class _ChildrenElementList implements ElementList {
     throw 'Not impl yet. todo(jacobr)';
   }
 
-  void setRange(int start, int length, List from, [int startFrom = 0]) {
-    throw const NotImplementedException();
-  }
+  void setRange(int start, int length, List from, [int startFrom = 0]) =>
+    Lists.setRange(this, start, length, from, startFrom);
 
-  void removeRange(int start, int length) {
-    throw const NotImplementedException();
-  }
+  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) {
-    throw const NotImplementedException();
-  }
+  List getRange(int start, int length) => Lists.getRange(this, start, length);
 
   int indexOf(Element element, [int start = 0]) {
-    return _Lists.indexOf(this, element, start, this.length);
+    return Lists.indexOf(this, element, start, this.length);
   }
 
   int lastIndexOf(Element element, [int start = null]) {
     if (start === null) start = length - 1;
-    return _Lists.lastIndexOf(this, element, start);
+    return Lists.lastIndexOf(this, element, start);
   }
 
   void clear() {