Fix flaky testZipInIncognito

testZipInIncognito occassionally fails because the download hasn't finished
yet. fix it.

BUG=
TEST=

Review URL: http://codereview.chromium.org/6275016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72393 0039d316-1c4b-4281-b951-d872f2087c98

chrome/test/functional/downloads.py

@@ -138,6 +138,9 @@ class DownloadsTest(pyauto.PyUITest):
     # Trigger download and wait in new incognito window.
     self.DownloadAndWaitForStart(file_url, 1)
     self.WaitForAllDownloadsToComplete(1)
+    # Remove next line when WaitForAllDownloadsToComplete can reliably wait
+    # for downloads in incognito window. crbug.com/69738
+    self.WaitForDownloadToComplete(downloaded_pkg)
     incognito_downloads = self.GetDownloadsInfo(1).Downloads()
 
     # Verify that download info exists in the correct profile.