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

git_cl.py

@@ -1593,8 +1593,7 @@ class _GerritChangelistImpl(_ChangelistCodereviewBase):
     raise NotImplementedError()
 
   def CloseIssue(self):
-    # TODO(tandrii)
-    raise NotImplementedError()
+    gerrit_util.AbandonChange(self._GetGerritHost(), self.GetIssue(), msg='')
 
 
 class ChangeDescription(object):