Make first and last getters.

samples/tests/samples/lib/observable/observable_list_tests.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 testObservableList() {
   test('ObservableList', () {
     final arr = new ObservableList<int>();
 
     // Add some initial data before listening
     arr.add(1);
@@ skipping 18 matching lines @@
     bool called = false;
     EventBatch.wrap((e) {
       expect(arr, hasLength(6));
       expect(arr[0], equals(1));
       // TODO(sigmund): why we need write startIndex? it should be optional.
       expect(arr.indexOf(4, 0), equals(5));
       expect(arr.indexOf(1, 0), equals(0));
       expect(arr.indexOf(1, 1), equals(3));
       // TODO(rnystrom): Get rid of second arg when lastIndexOf has default.
       expect(arr.lastIndexOf(1, arr.length - 1), equals(3));
-      expect(arr.last(), equals(4));
+      expect(arr.last, equals(4));
       final copy = new List<int>();
       arr.forEach(f(i) {
         copy.add(i);
       });
       expect(copy, orderedEquals([1, 2, 3, 1, 3, 4]));
       called = true;
     })(null);
     expect(called, isTrue);
     expect(res, isNull); // no change from read-only operators
 
@@ skipping 59 matching lines @@
       arr.clear();
       called = true;
     })(null);
     expect(called, isTrue);
     expect(res, isNotNull);
     expect(res.events, hasLength(1));
     validateGlobal(res.events[0], arr);
     expect(arr, orderedEquals([]));
   });
 }