Fix all strong mode errors and warnings.

test/selector_test.dart

 // Copyright (c) 2012, 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 selector_test;
 
 import 'package:csslib/parser.dart';
+import 'package:csslib/src/messages.dart';
 import 'package:test/test.dart';
 
 import 'testing.dart';
 
 void testSelectorSuccesses() {
-  var errors = [];
+  var errors = <Message>[];
   var selectorAst = selector('#div .foo', errors: errors);
   expect(errors.isEmpty, true, reason: errors.toString());
   expect('#div .foo', compactOuptut(selectorAst));
 
   // Valid selectors for class names.
   selectorAst = selector('.foo', errors: errors..clear());
   expect(errors.isEmpty, true, reason: errors.toString());
   expect('.foo', compactOuptut(selectorAst));
 
   selectorAst = selector('.foobar .xyzzy', errors: errors..clear());
@@ skipping 19 matching lines @@
   expect('#id-number-3', compactOuptut(selectorAst));
 
   selectorAst = selector('#_privateId', errors: errors..clear());
   expect(errors.isEmpty, true, reason: errors.toString());
   expect('#_privateId', compactOuptut(selectorAst));
 }
 
 // TODO(terry): Move this failure case to a failure_test.dart when the analyzer
 //              and validator exit then they'll be a bunch more checks.
 void testSelectorFailures() {
-  var errors = [];
+  var errors = <Message>[];
 
   // Test for invalid class name (can't start with number).
   selector('.foobar .1a-story .xyzzy', errors: errors);
   expect(errors.isEmpty, false);
   expect(errors[0].toString(),
       'error on line 1, column 9: name must start with a alpha character, but '
       'found a number\n'
       '.foobar .1a-story .xyzzy\n'
       '        ^^');
 }
 
 main() {
   test('Valid Selectors', testSelectorSuccesses);
   test('Invalid Selectors', testSelectorFailures);
 }