Add additional logging to diagnose flaky testZipInIncognito test

Review URL: http://codereview.chromium.org/6369010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72221 0039d316-1c4b-4281-b951-d872f2087c98

chrome/test/functional/downloads.py

@@ -142,7 +142,10 @@ class DownloadsTest(pyauto.PyUITest):
 
     # Verify that download info exists in the correct profile.
     self.assertEqual(len(incognito_downloads), 1)
-    self.assertTrue(self._EqualFileContents(file_path, downloaded_pkg))
+    self.assertTrue(self._EqualFileContents(file_path, downloaded_pkg),
+        msg='%s (size %d) and %s (size %d) do not match' % (
+            file_path, os.path.getsize(file_path),
+            downloaded_pkg, os.path.getsize(downloaded_pkg)))
     self.assertTrue(self.IsDownloadShelfVisible(1))
 
   def testSaveDangerousFile(self):