Add a simple fetch API test.

LayoutTests/http/tests/fetch/PRESUBMIT.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.
 
 '''Chromium presubmit script for fetch API layout tests.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts.
 '''
 
 import os
 import os.path
 import re
 
 
 def missing_files(scripts_path, top_path, worker_path):
     for script in os.listdir(scripts_path):
+        if script.startswith('.') or not script.endswith('.js'):
+            continue
         basename = re.sub(r'\.js$', '.html', os.path.basename(script))
-        window_path = os.path.join(top_path, basename)
-        worker_path = os.path.join(worker_path, basename)
-        for path in [window_path, worker_path]:
+        for path in [os.path.join(top_path, basename),
+                     os.path.join(worker_path, basename)]:
             if not os.path.exists(path):
                 yield path
 
 
 def CheckChangeOnUpload(input, output):
     top_path = input.PresubmitLocalPath()
     worker_path = os.path.join(top_path, 'workers')
     script_tests_path = os.path.join(top_path, 'script-tests')
 
     return [output.PresubmitPromptWarning('%s is missing' % path) for path
             in missing_files(script_tests_path, top_path, worker_path)]