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

base/platform_file_win.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 "base/platform_file.h"
 
 #include <io.h>
 
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ skipping 40 matching lines @@
     return NULL;
   }
 
   DWORD access = (flags & PLATFORM_FILE_READ) ? GENERIC_READ : 0;
   if (flags & PLATFORM_FILE_WRITE)
     access |= GENERIC_WRITE;
   if (flags & PLATFORM_FILE_WRITE_ATTRIBUTES)
     access |= FILE_WRITE_ATTRIBUTES;
   if (flags & PLATFORM_FILE_EXECUTE)
     access |= GENERIC_EXECUTE;
+  if (flags & PLATFORM_FILE_APPEND) {
+    access |= FILE_APPEND_DATA;
+    if (flags & PLATFORM_FILE_WRITE)  // Invalid.
+      return NULL;
+  }
 
   DWORD sharing = (flags & PLATFORM_FILE_EXCLUSIVE_READ) ? 0 : FILE_SHARE_READ;
   if (!(flags & PLATFORM_FILE_EXCLUSIVE_WRITE))
     sharing |= FILE_SHARE_WRITE;
   if (flags & PLATFORM_FILE_SHARE_DELETE)
     sharing |= FILE_SHARE_DELETE;
 
   DWORD create_flags = 0;
   if (flags & PLATFORM_FILE_ASYNC)
     create_flags |= FILE_FLAG_OVERLAPPED;
@@ skipping 215 matching lines @@
     case ERROR_DISK_CORRUPT:
       return PLATFORM_FILE_ERROR_IO;
     default:
       UMA_HISTOGRAM_SPARSE_SLOWLY("PlatformFile.UnknownErrors.Windows",
                                   last_error);
       return PLATFORM_FILE_ERROR_FAILED;
   }
 }
 
 }  // namespace base