Extract ResultCatcher from ExtensionApiTest. Use it in ShellApiTest.

chrome/test/data/extensions/api_test/dns/api/background.js

-// Copyright (c) 2012 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.
-
-var testIPLiteralResolution = function() {
-  var callback = function(resolveInfo) {
-    chrome.test.assertEq(0, resolveInfo.resultCode);
-    chrome.test.assertEq("127.0.0.1", resolveInfo.address);
-    chrome.test.succeed("IP literal resolved");
-  };
-  chrome.dns.resolve("127.0.0.1", callback);
-};
-
-var testHostnameResolution = function() {
-  var callback = function(resolveInfo) {
-    chrome.test.assertEq(0, resolveInfo.resultCode);
-    chrome.test.assertEq("9.8.7.6", resolveInfo.address);
-    chrome.test.succeed("hostname resolved");
-  };
-  chrome.dns.resolve("www.sowbug.com", callback);
-};
-
-var testNonexistentHostnameResolution = function() {
-  var callback = function(resolveInfo) {
-    // NET_ERROR(NAME_NOT_RESOLVED, -105)
-    chrome.test.assertEq(-105, resolveInfo.resultCode);
-    chrome.test.succeed("hostname correctly failed to resolve");
-  };
-  chrome.dns.resolve("this.hostname.is.bogus", callback);
-};
-
-chrome.test.runTests([testIPLiteralResolution,
-                      testHostnameResolution,
-                      testNonexistentHostnameResolution]);