Implement size and position support for launchWebAuthFlow.

chrome/test/data/extensions/api_test/identity/test.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 assertEq = chrome.test.assertEq;
-var pass = chrome.test.callbackPass;
-
-chrome.test.runTests([
-  function getAuthToken() {
-    chrome.experimental.identity.getAuthToken(
-        pass(function(token) {
-      assertEq('auth_token', token);
-    }));
-  },
-
-  function launchAuthFlow() {
-    chrome.experimental.identity.launchWebAuthFlow(
-        {url: 'https://some/url'},
-        pass(function(url) {
-      assertEq('https://abcd.chromiumapp.org/cb#access_token=tok', url);
-    }));
-  }
-]);