Add test of crypto.getRandomValues.

tests/html/crypto_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 crypto_test;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
+
+main() {
+  useHtmlConfiguration();
+
+  test('exists', () {
+    var crypto = window.crypto;
+    expect(crypto is Crypto, isTrue);
+  });
+
+  test('successful call', () {
+    var crypto = window.crypto;
+    var data = new Uint8Array(100);
+    expect(data.every((e) => e == 0), isTrue);
+    crypto.getRandomValues(data);
+    // In theory this is flaky. However, in practice you will get 100 zeroes
+    // in a row from a cryptographically secure random number generator so
+    // rarely that we don't have to worry about it.
+    expect(data.any((e) => e != 0), isTrue);
+  });
+
+  test('type mismatch', () {
+    var crypto = window.crypto;
+    var data = new Float32Array(100);
+    expect(() {
+      crypto.getRandomValues(data);
+    }, throws, reason: 'Only typed array views with integer types allowed');
+  });
+}