The handling of async IO on Windows wrongly casted everything to a socket connection. For named pipe based connections this caused reading of invalid memory.
Moved some of the functions to a common superclass and only call showdown for socket connections. For named pipe based connections the Dart part of the code will never send shutdown commands as named pipe based connections start out being closed in one direction and closing the other direction causes a close command.
R=ager@google.com
BUG=dart:363
TEST=
Review URL: http://codereview.chromium.org//8503006
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@1308 260f80e4-7a28-3924-810f-c04153c831b5
whesse@google.com