Removed Polymer from Observatory deps

packages/polymer_expressions/test/visitor_test.dart

-// Copyright (c) 2013, 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.
-
-library visitor_test;
-
-import 'package:polymer_expressions/parser.dart';
-import 'package:polymer_expressions/visitor.dart';
-import 'package:unittest/unittest.dart';
-
-main() {
-
-  group('visitor', () {
-
-    // regression test
-    test('should not infinitely recurse on parenthesized expressions', () {
-      var visitor = new TestVisitor();
-      var expr = new Parser('(1)').parse();
-      visitor.visit(expr);
-    });
-
-  });
-}
-
-class TestVisitor extends RecursiveVisitor {}