Add Stream.drain() method.

sdk/lib/async/stream.dart

Index: sdk/lib/async/stream.dart
diff --git a/sdk/lib/async/stream.dart b/sdk/lib/async/stream.dart
index 4be59b7326b09d1f0706db8ddf935b85f13c1097..1baaf014a4a463ff2e4774643f803a68304e8318 100644
--- a/sdk/lib/async/stream.dart
+++ b/sdk/lib/async/stream.dart
@@ -499,6 +499,12 @@ abstract class Stream<T> {
   }
 
   /**
+   * Discard all data on the stream, but signal when it's done or an error
+   * occoured.

[floitsch, 2013/05/24 11:50:42]

Discards ... signals ... occured

Add optional argument that will be the result of the future. (similar to
asFuture).

[Anders Johnsen, 2013/05/24 12:45:03]

Done.

+   */
+  Future drain() => listen(null).asFuture();

[floitsch, 2013/05/24 11:50:42]

list(null, cancelOnError: true), documenting that you take this approach.

[Anders Johnsen, 2013/05/24 12:45:03]

Done.

[Søren Gjesse, 2013/05/24 14:02:04]

Should it maybe have a named optional argument "ignoreError"?

[floitsch, 2013/05/24 16:21:33]

I think that this should be kept as simple as possible.
If you want more fancy behavior just write the 15 characters.

+
+  /**
    * Provides at most the first [n] values of this stream.
    *
    * Forwards the first [n] data events of this stream, and all error