Gerrit: make git cl close working.

BUG=579160

Review URL: https://codereview.chromium.org/1827523003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299465 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/git_cl.py b/git_cl.py
index 15f44a9..3c345e4 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -1593,8 +1593,7 @@
     raise NotImplementedError()
 
   def CloseIssue(self):
-    # TODO(tandrii)
-    raise NotImplementedError()
+    gerrit_util.AbandonChange(self._GetGerritHost(), self.GetIssue(), msg='')
 
 
 class ChangeDescription(object):