Add an "append flag" to base::PlatformFile.

base/platform_file.h

 // 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.
 
 #ifndef BASE_PLATFORM_FILE_H_
 #define BASE_PLATFORM_FILE_H_
 
 #include "build/build_config.h"
 #if defined(OS_WIN)
 #include <windows.h>
@@ skipping 31 matching lines @@
 
   PLATFORM_FILE_WRITE_ATTRIBUTES = 1 << 13,  // Used on Windows only
   PLATFORM_FILE_ENUMERATE = 1 << 14,         // May enumerate directory
 
   PLATFORM_FILE_SHARE_DELETE = 1 << 15,      // Used on Windows only
 
   PLATFORM_FILE_TERMINAL_DEVICE = 1 << 16,   // Serial port flags
   PLATFORM_FILE_BACKUP_SEMANTICS = 1 << 17,  // Used on Windows only
 
   PLATFORM_FILE_EXECUTE = 1 << 18,           // Used on Windows only
+
+  PLATFORM_FILE_APPEND = 1 << 19,
 };
 
 // PLATFORM_FILE_ERROR_ACCESS_DENIED is returned when a call fails because of
 // a filesystem restriction. PLATFORM_FILE_ERROR_SECURITY is returned when a
 // browser policy doesn't allow the operation to be executed.
 enum PlatformFileError {
   PLATFORM_FILE_OK = 0,
   PLATFORM_FILE_ERROR_FAILED = -1,
   PLATFORM_FILE_ERROR_IN_USE = -2,
   PLATFORM_FILE_ERROR_EXISTS = -3,
@@ skipping 178 matching lines @@
     return temp;
   }
 
  private:
   PlatformFile* value_;
 };
 
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_