headless: Avoid copies for string parameters in DevTools bindings

headless/lib/browser/devtools_api/client_api_generator_unittest.py

 #!/usr/bin/env python
 
 # Copyright 2016 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 client_api_generator
 import shutil
 import sys
 import tempfile
@@ skipping 129 matching lines @@
               'type': 'string',
             },
           ]
         },
       ]
     }
     client_api_generator.CreateTypeDefinitions(json_api)
     type = json_api['domains'][0]['types'][0]
     resolved = client_api_generator.ResolveType(type)
     self.assertEqual('std::string', resolved['raw_type'])
+    self.assertEqual('const std::string&', resolved['pass_type'])
 
   def test_ObjectType(self):
     json_api = {
       'domains': [
         {
           'domain': 'domain',
           'types': [
             {
               'id': 'TestType',
               'type': 'object',
@@ skipping 390 matching lines @@
           jinja_env, dirname, json_api,
           'domain', ['cc', 'h'], lambda domain_name: domain_name)
       # This is just a smoke test; we don't actually verify the generated output
       # here.
     finally:
       shutil.rmtree(dirname)
 
 
 if __name__ == '__main__':
   unittest.main(verbosity=2, exit=False, argv=sys.argv)