Add StreamChannel.withGuarantees and StreamChannelController.

CHANGELOG.md

Index: CHANGELOG.md
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 813870874326a3d144d3028183563fee84f65527..0b61d81f8e457142eb671e02d64091526c95c1f7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,11 @@
+## 1.2.0
+
+* Add `new StreamChannel.withGuarantees()`, which creates a channel with extra
+  wrapping to ensure that it obeys the stream channel guarantees.
+
+* Add `StreamChannelController`, which can be used to create custom
+  `StreamChannel` objects.
+
 ## 1.1.1
 
 * Fix the type annotation for `StreamChannel.transform()`'s parameter.