Fix closing of server sockets.
Fix closing of server sockets.

Waiting for the onClosed event on the socket output stream is the
right thing to do. However, only if we actually make sure that it
will always close. :-)

R=sgjesse@google.com,ajohnsen@google.com
BUG=

Review URL: https://chromiumcodereview.appspot.com//10914200

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@12199 260f80e4-7a28-3924-810f-c04153c831b5

dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk