Remove StreamSink(replaced by EventSink) and make IOSink extend EventSink.
Remove StreamSink(replaced by EventSink) and make IOSink extend EventSink.

With this change 'writeBytes' was renamed to 'add'.

BUG=

Review URL: https://codereview.chromium.org//14150002

git-svn-id: a0fc6a377c96b9059f80895148836233a16d98be@21275 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/http,dart-lang/http,dart-lang/http,dart-lang/http,dart-lang/http,dart-lang/http,kasperpeulen/http,donny-dont/http,dart-lang/http,dart-lang/http