Do not call check-webkit-style with empty affected file list as it tries to check all edited files …

third_party/WebKit/PRESUBMIT.py

 # Copyright (c) 2013 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.
 
 """Top-level presubmit script for Blink.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 119 matching lines @@
         if errs.strip() != 'Lint succeeded.':
             return [output_api.PresubmitError(errs)]
     return []
 
 
 def _CheckStyle(input_api, output_api):
     # Files that follow Chromium's coding style do not include capital letters.
     re_chromium_style_file = re.compile(r'\b[a-z_]+\.(cc|h)$')
     style_checker_path = input_api.os_path.join(input_api.PresubmitLocalPath(),
         'Tools', 'Scripts', 'check-webkit-style')
-    args = ([input_api.python_executable, style_checker_path, '--diff-files']
-            + [input_api.os_path.join('..', '..', f.LocalPath())
-               for f in input_api.AffectedFiles()
-               # Filter out files that follow Chromium's coding style.
-               if not re_chromium_style_file.search(f.LocalPath())])
+    args = [input_api.python_executable, style_checker_path, '--diff-files']
+    files = [input_api.os_path.join('..', '..', f.LocalPath())
+             for f in input_api.AffectedFiles()
+             # Filter out files that follow Chromium's coding style.
+             if not re_chromium_style_file.search(f.LocalPath())]
+    # Do not call check-webkit-style with empty affected file list if all
+    # input_api.AffectedFiles got filtered.
+    if not files:
+        return []
+    args += files
     results = []
 
     try:
         child = input_api.subprocess.Popen(args,
                                            stderr=input_api.subprocess.PIPE)
         _, stderrdata = child.communicate()
         if child.returncode != 0:
             results.append(output_api.PresubmitError(
                 'check-webkit-style failed', [stderrdata]))
     except Exception as e:
@@ skipping 211 matching lines @@
     new_description = description
     new_description += '\nCQ_INCLUDE_TRYBOTS=%s' % ';'.join(bots)
     results.append(output_api.PresubmitNotifyResult(
         'Automatically added slimming-paint-v2 tests to run on CQ due to '
         'changes in paint or compositing directories.'))
 
     if new_description != description:
         rietveld_obj.update_description(issue, new_description)
 
     return results