sysmon: Fix typo

BUG=chromium:724580
BUG=chromium:736911
TEST=None

Change-Id: I6ce8383fa04e7433204d2a1066b8264364a7f139
Reviewed-on: https://chromium-review.googlesource.com/549183
Reviewed-by: Paul Hobbs <phobbs@google.com>
Commit-Queue: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Trybot-Ready: Allen Li <ayatane@chromium.org>
diff --git a/scripts/sysmon/git_metrics.py b/scripts/sysmon/git_metrics.py
index a0aa7d4..ee7cca3 100644
--- a/scripts/sysmon/git_metrics.py
+++ b/scripts/sysmon/git_metrics.py
@@ -105,7 +105,7 @@
     self._timestamp_metric.set(commit_time, self._fields)
 
   def _collect_unstaged_changes_metric(self):
-    added, deleted = self._gitrepo.get_commit_time()
+    added, deleted = self._gitrepo.get_unstaged_changes()
     self._timestamp_metric.set(
         added, fields=dict(change_type='added', **self._fields))
     self._timestamp_metric.set(