Add licensing header to git-try.

TBR=maruel
Review URL: http://codereview.chromium.org/177047

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@24994 0039d316-1c4b-4281-b951-d872f2087c98

git-try

@@ -1,4 +1,7 @@
 #!/usr/bin/python
+# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
 
 import getpass
 import optparse