Change the CQ code to update R= line as done in depot_tools.

pending_manager.py

Index: pending_manager.py
diff --git a/pending_manager.py b/pending_manager.py
index 49e4ae58150e4a561c31d6a77b2056d2d73c3b8d..391a6d1f26c4c7aea669aef880cbee6108083003 100644
--- a/pending_manager.py
+++ b/pending_manager.py
@@ -442,9 +442,11 @@ class PendingManager(object):
         pending.apply_patch(self.context, True)
         # Commit it.
         commit_desc = git_cl.ChangeDescription(pending.description)
+        props = {'reviewers': pending.reviewers, 'messages': pending.messages}
+        approving_reviewers = git_cl.get_approving_reviewers(props)
+        commit_desc.update_reviewers(approving_reviewers)
         if (self.context.server_hooks_missing and
             self.context.rietveld.email != pending.owner):
-          commit_desc.update_reviewers(pending.reviewers)
           commit_desc.append_footer('Author: ' + pending.owner)
         commit_desc.append_footer('Review URL: %s/%s' % (
             self.context.rietveld.url,
@@ -461,6 +463,7 @@ class PendingManager(object):
 
         viewvc_url = self.context.checkout.get_settings('VIEW_VC')
         issue_desc = git_cl.ChangeDescription(pending.description)
+        issue_desc.update_reviewers(approving_reviewers)
         msg = 'Committed: %s' % pending.revision
         if viewvc_url:
           viewvc_url = '%s%s' % (viewvc_url.rstrip('/'), pending.revision)