Docserver: Make MockFileSystem not iterate over the entire file system as part

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

Index: chrome/common/extensions/docs/server2/empty_dir_file_system.py
diff --git a/chrome/common/extensions/docs/server2/empty_dir_file_system.py b/chrome/common/extensions/docs/server2/empty_dir_file_system.py
index 58053a80f57f50e8413797ff8d1ccdcd0cc6ce3c..24a5a26fe32c5642fbaf56dd825828c4f9171080 100644
--- a/chrome/common/extensions/docs/server2/empty_dir_file_system.py
+++ b/chrome/common/extensions/docs/server2/empty_dir_file_system.py
@@ -4,6 +4,8 @@
 
 from file_system import FileNotFoundError, FileSystem, StatInfo
 from future import Future
+from path_util import IsDirectory
+
 
 class EmptyDirFileSystem(FileSystem):
   '''A FileSystem with empty directories. Useful to inject places to disable
@@ -12,7 +14,7 @@ class EmptyDirFileSystem(FileSystem):
   def Read(self, paths):
     result = {}
     for path in paths:
-      if not path.endswith('/'):
+      if not IsDirectory(path):
         raise FileNotFoundError('EmptyDirFileSystem cannot read %s' % path)
       result[path] = []
     return Future(value=result)
@@ -21,7 +23,7 @@ class EmptyDirFileSystem(FileSystem):
     return Future(value=())
 
   def Stat(self, path):
-    if not path.endswith('/'):
+    if not IsDirectory(path):
       raise FileNotFoundError('EmptyDirFileSystem cannot stat %s' % path)
     return StatInfo(0, child_versions=[])