Make first and last getters.

tests/html/htmlcollection_test.dart

 #library('ElementListTest');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 // Test that List<Element> implements List<T>
 main() {
   Element insertTestDiv() {
     Element element = new Element.tag('div');
     element.innerHTML = r"""
@@ skipping 193 matching lines @@
     root.remove();
   });
   test('Last', () {
     Element root = insertTestDiv();
 
     List<Element> someChecked =
         document.query('#someChecked').elements;
 
     Expect.equals(4, someChecked.length);
 
-    Expect.equals(someChecked[3], someChecked.last());
+    Expect.equals(someChecked[3], someChecked.last);
 
     root.remove();
   });
   test('IndexOf', () {
     Element root = insertTestDiv();
 
     List<Element> someChecked =
         document.query('#someChecked').elements;
 
     List<Element> noneChecked =
@@ skipping 43 matching lines @@
     Expect.equals(-1, someChecked.lastIndexOf(someChecked[3], 2));
 
     Expect.equals(-1, someChecked.lastIndexOf(noneChecked[0], 3));
     Expect.equals(-1, noneChecked.lastIndexOf(someChecked[0], 3));
     Expect.equals(-1, someChecked.lastIndexOf(noneChecked[1], 3));
     Expect.equals(-1, noneChecked.lastIndexOf(someChecked[1], 3));
 
     root.remove();
   });
 }