Fix typo in stream.dart.

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 f6b235a9a61f52f75ef10668a75fdedfe87d1269..dff5b18f984c28548898c94bc96448666331c02a 100644
--- a/sdk/lib/async/stream.dart
+++ b/sdk/lib/async/stream.dart
@@ -1493,7 +1493,7 @@ abstract class StreamConsumer<S> {
   Future addStream(Stream<S> stream);
 
   /**
-   * Tells the consumer that no futher streams will be added.
+   * Tells the consumer that no further streams will be added.
    *
    * This allows the consumer to complete any remaining work and release
    * resources that are no longer needed
@@ -1527,7 +1527,7 @@ abstract class StreamConsumer<S> {
  */
 abstract class StreamSink<S> implements EventSink<S>, StreamConsumer<S> {
   /**
-   * Tells the stream sink that no futher streams will be added.
+   * Tells the stream sink that no further streams will be added.
    *
    * This allows the stream sink to complete any remaining work and release
    * resources that are no longer needed