Add a bunch of delegates for dart:async types.

CHANGELOG.md

Index: CHANGELOG.md
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ab118014be4d031f0950b2b6411cadf6dca7be65..6a7f9e151ff14aeb4b85bf9228c9cfdfa39ea441 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,13 +7,16 @@
   before they are avilable. It is like a `StreamIterator` that can queue
   requests.
 
-- Added `DelegatingStreamSubscription` which is a simple wrapper around
-  a `StreamSubscription` that forwards all call to the wrapped subscription.
-  It can be extended to wrap extra functionality around a subscription.
-
 - Added `SubscriptionStream` which creates a single-subscription stream
   from an existing stream subscription.
 
+- Added delegating wrapper classes for a number of core async types:
+  `DelegatingFuture`, `DelegatingStreamConsumer`, `DelegatingStreamController`,
+  `DelegatingSink`, `DelegatingEventSink`, `DelegatingStreamSink`, and
+  `DelegatingStreamSubscription`. These are all simple wrappers that forward all
+  calls to the wrapped objects. They can be used to expose only the desired
+  interface for subclasses, or extended to add extra functionality.
+
 ## 1.2.0
 
 - Added a `FutureGroup` class for waiting for a group of futures, potentially of