Add a bunch of delegates for dart:async types.

CHANGELOG.md

 ## 1.3.0
 
 - Added `StreamCompleter` class for creating a stream now and providing its
   events later as another stream.
 
 - Added `StreamQueue` class which allows requesting events from a stream
   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
   unknown size, to complete.
 
 - Added a `StreamGroup` class for merging the events of a group of streams,
   potentially of unknown size.
 
 ## 1.1.1
 
 - Updated SDK version constraint to at least 1.9.0.
 
 ## 1.1.0
 
 - ChangeLog starts here.