Presubmit: Skip third_party for fwd decl warning

PRESUBMIT_test_mocks.py

 # Copyright 2014 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 json
 import os
 import re
 import subprocess
 import sys
 
@@ skipping 102 matching lines @@
   def NewContents(self):
     return self._new_contents
 
   def LocalPath(self):
     return self._local_path
 
   def AbsoluteLocalPath(self):
     return self._local_path
 
   def GenerateScmDiff(self):
-    return self._scm_diff;
+    return self._scm_diff
 
   def rfind(self, p):
     """os.path.basename is called on MockFile so we need an rfind method."""
     return self._local_path.rfind(p)
 
   def __getitem__(self, i):
     """os.path.basename is called on MockFile so we need a get method."""
     return self._local_path[i]
 
   def __len__(self):
@@ skipping 15 matching lines @@
 
   def __init__(self, changed_files):
     self._changed_files = changed_files
 
   def LocalPaths(self):
     return self._changed_files
 
   def AffectedFiles(self, include_dirs=False, include_deletes=True,
                     file_filter=None):
     return self._changed_files