Add CachingFileSystem on top of CloudStorageFileSystem

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

Index: chrome/common/extensions/docs/server2/gcs_file_system_provider.py
diff --git a/chrome/common/extensions/docs/server2/gcs_file_system_provider.py b/chrome/common/extensions/docs/server2/gcs_file_system_provider.py
index 3ea535d1299f5dd778546f9137fe7c0cca80568b..3d60084d2252a841eae573d374bb22acc2f43d85 100644
--- a/chrome/common/extensions/docs/server2/gcs_file_system_provider.py
+++ b/chrome/common/extensions/docs/server2/gcs_file_system_provider.py
@@ -5,6 +5,7 @@
 import os
 import environment
 
+from caching_file_system import CachingFileSystem
 from empty_dir_file_system import EmptyDirFileSystem
 from extensions_paths import LOCAL_GCS_DIR, LOCAL_GCS_DEBUG_CONF
 from local_file_system import LocalFileSystem
@@ -81,9 +82,9 @@ class CloudStorageFileSystemProvider(object):
     # gcs_file_system has strong dependencies on runtime appengine APIs,
     # so we only import it when we are sure we are not on preview.py or tests.
     from gcs_file_system import CloudStorageFileSystem
-    return CloudStorageFileSystem(
-        bucket, debug_access_token, debug_bucket_prefix)
-
+    return CachingFileSystem(CloudStorageFileSystem(bucket,
+        debug_access_token, debug_bucket_prefix),
+        self._object_store_creator)
 
   @staticmethod
   def ForEmpty():