Convert more interfaces to the new thunk system. This goes up to and including

ppapi/thunk/ppb_file_system_api.h

 // Copyright (c) 2011 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 PPAPI_THUNK_PPB_FILE_SYSTEM_API_H_
 #define PPAPI_THUNK_PPB_FILE_SYSTEM_API_H_
 
 #include "ppapi/c/dev/ppb_file_system_dev.h"
 
 namespace ppapi {
 namespace thunk {
 
 class PPB_FileSystem_API {
  public:
   virtual int32_t Open(int64_t expected_size,
                        PP_CompletionCallback callback) = 0;
   virtual PP_FileSystemType_Dev GetType() = 0;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_PPB_FILE_SYSTEM_API_H_