Check include order on cpp files as well

PRESUBMIT.py

 # Copyright 2015 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.
 
 """Presubmit script for pdfium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
@@ skipping 221 matching lines @@
 
   Each region separated by #if, #elif, #else, #endif, #define and #undef follows
   these rules separately.
   """
   def FileFilterIncludeOrder(affected_file):
     black_list = (input_api.DEFAULT_BLACK_LIST)
     return input_api.FilterSourceFile(affected_file, black_list=black_list)
 
   warnings = []
   for f in input_api.AffectedFiles(file_filter=FileFilterIncludeOrder):
-    if f.LocalPath().endswith(('.cc', '.h', '.mm')):
+    if f.LocalPath().endswith(('.cc', '.cpp', '.h', '.mm')):
       changed_linenums = set(line_num for line_num, _ in f.ChangedContents())
       warnings.extend(_CheckIncludeOrderInFile(input_api, f, changed_linenums))
 
   results = []
   if warnings:
     results.append(output_api.PresubmitPromptOrNotify(_INCLUDE_ORDER_WARNING,
                                                       warnings))
   return results
 
 
 def CheckChangeOnUpload(input_api, output_api):
   results = []
   results += _CheckUnwantedDependencies(input_api, output_api)
   results += input_api.canned_checks.CheckPatchFormatted(input_api, output_api)
   results += input_api.canned_checks.CheckChangeLintsClean(
       input_api, output_api, None, LINT_FILTERS)
   results += _CheckIncludeOrder(input_api, output_api)
 
   return results