Switch FlushCallback to be a PP_CompletionCallback....

c/pp_errors.h

 // Copyright (c) 2010 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_C_PP_ERRORS_H_
 #define PPAPI_C_PP_ERRORS_H_
 
 // Errors are negative valued.
 enum {
   PP_OK = 0,
@@ skipping 24 matching lines @@
   PP_Error_NoAccess = -7,
 
   // Indicates failure due to insufficient memory.
   PP_Error_NoMemory = -8,
 
   // Indicates failure due to insufficient storage space.
   PP_Error_NoSpace = -9,
 
   // Indicates failure due to insufficient storage quota.
   PP_Error_NoQuota = -10,
+
+  // Indicates failure due to an action already being in progress.
+  PP_Error_InProgress = -11,
  
   // Indicates failure due to a file that does not exist.
   PP_Error_FileNotFound = -20,
 
   // Indicates failure due to a file that already exists.
   PP_Error_FileExists = -21,
 
   // Indicates failure due to a file that is too big.
   PP_Error_FileTooBig = -22,
 
   // Indicates failure due to a file having been modified unexpectedly.
   PP_Error_FileChanged = -23,
  
   // Indicates failure due to a time limit being exceeded.
   PP_Error_TimedOut = -30,
 };
 
 #endif  // PPAPI_C_PP_ERRORS_H_