Don't close existing connection on HttpServer close (and stream cancel).

sdk/lib/io/http.dart

Index: sdk/lib/io/http.dart
diff --git a/sdk/lib/io/http.dart b/sdk/lib/io/http.dart
index 76fe61901ff479d1e9c767244f662fcbeed02e79..2d311614465aaf4228ade4282b6fc8477fe016ea 100644
--- a/sdk/lib/io/http.dart
+++ b/sdk/lib/io/http.dart
@@ -171,12 +171,14 @@ abstract class HttpServer implements Stream<HttpRequest> {
 
   /**
    * Permanently stops this [HttpServer] from listening for new
-   * connections.  This closes this [Stream] of [HttpRequest]s with a
+   * connections.  This closes the [Stream] of [HttpRequest]s with a
    * done event. The returned future completes when the server is
    * stopped. For a server started using [bind] or [bindSecure] this
    * means that the port listened on no longer in use.
+   *
+   * If [force] is `true`, active connections will be closed immediately.
    */
-  Future close();
+  Future close({bool force: false});
 
   /**
    * Returns the port that the server is listening on. This can be