Add argument use_poll=True to asyncore.loop() calls in perf_snapshot.py.

chrome/test/functional/perf_endure.py

Index: chrome/test/functional/perf_endure.py
diff --git a/chrome/test/functional/perf_endure.py b/chrome/test/functional/perf_endure.py
index 431dad66d1d91875e45135a3bde4250d2818c00f..10364770d887f09e1b9419ce8edd08c6d59d42ef 100644
--- a/chrome/test/functional/perf_endure.py
+++ b/chrome/test/functional/perf_endure.py
@@ -73,7 +73,9 @@ class ChromeEndureBaseTest(perf.BasePerfTest):
           tab_proc_info.append(proc_info)
     self.assertEqual(len(tab_proc_info), 1,
                      msg='Expected to find 1 %s tab process, but found %d '
-                         'instead.' % (tab_title_substring, len(tab_proc_info)))
+                         'instead.\nCurrent process info:\n%s.' % (
+                         tab_title_substring, len(tab_proc_info),
+                         self.pformat(info)))
     tab_proc_info = tab_proc_info[0]
     return {
       'private_mem': tab_proc_info['working_set_mem']['priv']