Add gn args to metadata and metadata diffing

tools/binary_size/integration_test.py

 #!/usr/bin/env python
 # Copyright 2017 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 copy
 import difflib
 import itertools
 import logging
 import os
@@ skipping 69 matching lines @@
   def test_ConsoleNullDiff(self):
     with tempfile.NamedTemporaryFile(suffix='.size') as temp_file:
       file_format.SaveSizeInfo(self._CloneSizeInfo(), temp_file.name)
       return _RunApp('console.py', '--query', 'Diff(size_info1, size_info2)',
                      temp_file.name, temp_file.name)
 
   @_CompareWithGolden
   def test_ActualDiff(self):
     map1 = self._CloneSizeInfo()
     map2 = self._CloneSizeInfo()
+    map1.metadata = {"foo": 1, "bar": [1,2,3], "baz": "yes"}
+    map2.metadata = {"foo": 1, "bar": [1,3], "baz": "yes"}
     map1.symbols -= map1.symbols[0]
     map2.symbols -= map2.symbols[-1]
     map1.symbols[1].size -= 10
     diff = models.Diff(map1, map2)
     return describe.GenerateLines(diff, verbose=True)
 
   @_CompareWithGolden
   def test_SymbolGroupMethods(self):
     all_syms = self._CloneSizeInfo().symbols
     global_syms = all_syms.WhereNameMatches('GLOBAL')
@@ skipping 22 matching lines @@
   if len(argv) > 1 and argv[1] == '--update':
     argv.pop(0)
     global update_goldens
     update_goldens = True
 
   unittest.main(argv=argv, verbosity=2)
 
 
 if __name__ == '__main__':
   main()