Support automatic javascript test registry in gtest when creating WebUI tests.

chrome/test/data/webui/sample_pass.js

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Sample tests that exercise the test JS library and show how this framework
+// could be used to test the downloads page.
+function testAssertFalse() {
+  assertFalse(false);
+}
+
+function testAssertTrue() {
+  assertTrue(true);
+}
+
+function testAssertEquals() {
+  assertEquals(5, 5, "fives");
+}
+
+var test_fixture = 'WebUIBrowserTestPass';