[ew] Move operation observers from QuotaUtil to FileSystemBackend.

storage/browser/fileapi/isolated_file_system_backend.cc

 // 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.
 
 #include "storage/browser/fileapi/isolated_file_system_backend.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
@@ skipping 131 matching lines @@
           url.path(),
           offset,
           FileStreamWriter::OPEN_EXISTING_FILE));
 }
 
 FileSystemQuotaUtil* IsolatedFileSystemBackend::GetQuotaUtil() {
   // No quota support.
   return NULL;
 }
 
+const UpdateObserverList* IsolatedFileSystemBackend::GetUpdateObservers(
+    FileSystemType type) const {
+  return NULL;
+}
+
+const ChangeObserverList* IsolatedFileSystemBackend::GetChangeObservers(
+    FileSystemType type) const {
+  return NULL;
+}
+
+const AccessObserverList* IsolatedFileSystemBackend::GetAccessObservers(
+    FileSystemType type) const {
+  return NULL;
+}
+
 }  // namespace storage