[chrome-devtools-frontend] Migrate to cloudstorage client

gae/file_reader.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.
 
-from google.appengine.api import files
+import cloudstorage
 import logging
 import traceback
 
 import cache
 
 def read(config_helper, file_name):
   content = cache.get_content(file_name)
   if content:
     return content
   # Sometimes remote calls fail for different reasons. Make sure we retry.
   full_path = config_helper.get_full_path(file_name)
-  for _ in [1, 2, 3]:
-    try:
-      with files.open(full_path, 'r') as stream:
-        content = stream.read()
-        cache.set_content(file_name, content)
-        return content
-    except:
-      logging.error('Full path: %s' % full_path)
-      logging.error(traceback.format_exc())
+  try:
+    with cloudstorage.open(full_path, 'r') as stream:
+      content = stream.read()
+      cache.set_content(file_name, content)
+      return content
+  except:
+    logging.error('Full path: %s' % full_path)
+    logging.error(traceback.format_exc())
   return None