Try to fix clang plugin tests after https://codereview.chromium.org/2270433002/

tools/clang/plugins/tests/test.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 argparse
 import os
 import subprocess
 import sys
 
 script_dir = os.path.dirname(os.path.realpath(__file__))
 tool_dir = os.path.abspath(os.path.join(script_dir, '../../pylib'))
 sys.path.insert(0, tool_dir)
 
 from clang import plugin_testing
 
 
 class ChromeStylePluginTest(plugin_testing.ClangPluginTest):
   """Test harness for the Chrome style plugin."""
 
   def AdjustClangArguments(self, clang_cmd):
-    self.AddPluginArg(clang_cmd, 'follow-macro-expansion')
     clang_cmd.extend([
         # Skip code generation
         '-fsyntax-only',
         # Fake system directory for tests
         '-isystem', os.path.join(os.getcwd(), 'system'),
         '-Wno-inconsistent-missing-override',
     ])
 
 
 def main():
@@ skipping 11 matching lines @@
   return ChromeStylePluginTest(
       os.path.dirname(os.path.realpath(__file__)),
       args.clang_path,
       args.plugin_path,
       'find-bad-constructs',
       args.reset_results).Run()
 
 
 if __name__ == '__main__':
   sys.exit(main())