Add List.first.

sdk/lib/html/templates/immutable_list_mixin.darttemplate

   // -- start List<$E> mixins.
   // $E is the element type.
 
   // From Iterable<$E>:
 
   Iterator<$E> iterator() {
     // Note: NodeLists are not fixed size. And most probably length shouldn't
     // be cached in both iterator _and_ forEach method. For now caching it
     // for consistency.
     return new FixedSizeListIterator<$E>(this);
@@ skipping 39 matching lines @@
   }
 
   int indexOf($E element, [int start = 0]) =>
       _Lists.indexOf(this, element, start, this.length);
 
   int lastIndexOf($E element, [int start]) {
     if (start == null) start = length - 1;
     return _Lists.lastIndexOf(this, element, start);
   }
 
+  $E get first => this[0];
+
   $E get last => this[length - 1];
 
   $E removeLast() {
     throw new UnsupportedError("Cannot removeLast on immutable List.");
   }
 
   void setRange(int start, int rangeLength, List<$E> from, [int startFrom]) {
     throw new UnsupportedError("Cannot setRange on immutable List.");
   }
 
   void removeRange(int start, int rangeLength) {
     throw new UnsupportedError("Cannot removeRange on immutable List.");
   }
 
   void insertRange(int start, int rangeLength, [$E initialValue]) {
     throw new UnsupportedError("Cannot insertRange on immutable List.");
   }
 
   List<$E> getRange(int start, int rangeLength) =>
       _Lists.getRange(this, start, rangeLength, <$E>[]);
 
   // -- end List<$E> mixins.