Disable passwords.py Pyauto tests on Mac due to Keychain popups

chrome/test/functional/PYAUTO_TESTS

 # Copyright (c) 2010 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.
 #
 # This file lists the pyauto tests that run as a part of the functional test
 # suite.
 #
 # Tests can be enabled on a per-platform basis. Tests not listed here will
 # not be run.
 #
@@ skipping 29 matching lines @@
     'test_basic.SimpleTest.testCanOpenGoogle',
     'themes',
   ],
 
   'win': [
     # testBookmarkBarVisible fails on windows. crbug.com/42823
     '-bookmark_bar.BookmarkBarTest.testBookmarkBarVisible',
   ],
 
   'mac': [
+    # Keychain popups make password tests difficult. crbug.com/49378
+    '-passwords',
   ],
 
   'linux': [
     '-omnibox',  # http://crbug.com/44203
     '-browser.BrowserTest.testWindowResize',  # crbug.com/44963
     '-content.ContentTest.testThreeWindows',  # crbug.com/47457
   ],
 
   # TODO(nirnimesh): Add a ChromeOS section
 }