gclient: Add '--auto_rebase' sync option.

This adds the '--auto_rebase' sync option, enabling parallel updates to
automatically rebase local Git branches during sync.

BUG=None
TEST=local

Review URL: https://codereview.chromium.org/930693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@294151 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/tests/gclient_scm_test.py b/tests/gclient_scm_test.py
index 967d360..03a87fd 100755
--- a/tests/gclient_scm_test.py
+++ b/tests/gclient_scm_test.py
@@ -804,6 +804,7 @@
   """This class doesn't use pymox."""
   class OptionsObject(object):
     def __init__(self, verbose=False, revision=None):
+      self.auto_rebase = False
       self.verbose = verbose
       self.revision = revision
       self.manually_grab_svn_rev = True