[fsp] Add support for reading directories.

chrome/browser/chromeos/file_system_provider/provided_file_system_interface.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_
 
 #include "webkit/browser/fileapi/async_file_util.h"
 
 class EventRouter;
@@ skipping 18 matching lines @@
   // Requests unmounting of the file system. The callback is called when the
   // request is accepted or rejected, with an error code.
   virtual void RequestUnmount(
       const fileapi::AsyncFileUtil::StatusCallback& callback) = 0;
 
   // Requests metadata of the passed |entry_path|. It can be either a file
   // or a directory.
   virtual void GetMetadata(
       const base::FilePath& entry_path,
       const fileapi::AsyncFileUtil::GetFileInfoCallback& callback) = 0;
+  // Requests enumerating entries from the passed |directory_path|. The callback
+  // can be called multiple times until either an error is returned or the
+  // has_more field is set to false.
+  virtual void ReadDirectory(
+      const base::FilePath& directory_path,
+      const fileapi::AsyncFileUtil::ReadDirectoryCallback& callback) = 0;
 
   // Returns a provided file system info for this file system.
   virtual const ProvidedFileSystemInfo& GetFileSystemInfo() const = 0;
 
   // Returns a request manager for the file system.
   virtual RequestManager* GetRequestManager() = 0;
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_