Disabling downloads pyauto test on Windows that's flaky

BUG=83942
TEST=downloads.DownloadsTest.testDownloadsPersistence
Review URL: http://codereview.chromium.org/7053024

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@86725 0039d316-1c4b-4281-b951-d872f2087c98

chrome/test/functional/PYAUTO_TESTS

@@ -93,6 +93,7 @@
       # crbug.com/50481, crbug.com/54942
       '-downloads.DownloadsTest.testZip',
       '-downloads.DownloadsTest.testRemoveDownload',
+      '-downloads.DownloadsTest.testDownloadsPersistence',  # crbug.com/83942
       # crbug.com/66072
       '-notifications.NotificationsTest.testNotificationOrderAfterClosingOne',
       # crbug.com/70694, crbug.com/73078