Docserver: Add more skip_not_found support and cache "not found"s

chrome/common/extensions/docs/server2/local_file_system.py

 # Copyright (c) 2012 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 os
 import sys
 
 from docs_server_utils import StringIdentity
 from file_system import FileSystem, FileNotFoundError, StatInfo
 from future import Future
@@ skipping 70 matching lines @@
   def Read(self, paths, skip_not_found=False):
     def resolve():
       result = {}
       for path in paths:
         AssertIsValid(path)
         full_path = os.path.join(self._base_path,
                                  _ConvertToFilepath(path).lstrip(os.sep))
         if path == '' or path.endswith('/'):
           result[path] = _ListDir(full_path)
         else:
-          result[path] = _ReadFile(full_path)
+          try:
+            result[path] = _ReadFile(full_path)
+          except FileNotFoundError:
+            if skip_not_found:
+              continue
+            return Future(exc_info=sys.exc_info())
       return result
     return Future(callback=resolve)
 
   def Refresh(self):
     return Future(value=())
 
   def Stat(self, path):
     AssertIsValid(path)
     full_path = os.path.join(self._base_path,
                              _ConvertToFilepath(path).lstrip(os.sep))
     return _CreateStatInfo(full_path)
 
   def GetIdentity(self):
     return '@'.join((self.__class__.__name__, StringIdentity(self._base_path)))
 
   def __repr__(self):
     return 'LocalFileSystem(%s)' % self._base_path