Make `TypeSafeStream` extend `Stream`.

Make `TypeSafeStream` extend `Stream`.

This makes it automatically compatible with future additions to `Stream`,
like the `groupBy` method which will be added in SDK version 1.24.
It inherits the default implementation, which will use the `listen` method
of the `TypeSafeStream`, returning a `TypeSafeStreamSubscription`, and will
just have a type check for each event before the listener even sees it.

BUG=
R=floitsch@google.com

Committed: https://github.com/dart-lang/async/commit/daf66909019d2aaec1721fc39d94ea648a9fdc1d

[Lasse Reichstein Nielsen, 2017-05-10 07:48:20]

lrn@google.com changed reviewers:
+ floitsch@google.com

[floitsch, 2017-05-16 09:01:18]

LGTM.

https://codereview.chromium.org/2872233002/diff/1/lib/src/typed/stream.dart
File lib/src/typed/stream.dart (right):

https://codereview.chromium.org/2872233002/diff/1/lib/src/typed/stream.dart#n...
lib/src/typed/stream.dart:13: class TypeSafeStream<T> extends Stream<T> {
should we add `groupBy` as an optimization?

[floitsch, 2017-05-16 12:55:52]

Description was changed from

==========
Make `TypeSafeStream` extend `Stream`.

This makes it automatically compatible with future additions to `Stream`,
like the `groupBy` method which will be added in SDK version 1.24.
It inherits the default implementation, which will use the `listen` method
of the `TypeSafeStream`, returning a `TypeSafeStreamSubscription`, and will
just have a type check for each event before the listener even sees it.

BUG=
==========

to

==========
Make `TypeSafeStream` extend `Stream`.

This makes it automatically compatible with future additions to `Stream`,
like the `groupBy` method which will be added in SDK version 1.24.
It inherits the default implementation, which will use the `listen` method
of the `TypeSafeStream`, returning a `TypeSafeStreamSubscription`, and will
just have a type check for each event before the listener even sees it.

BUG=
R=floitsch@google.com

Committed:
https://github.com/dart-lang/async/commit/daf66909019d2aaec1721fc39d94ea648a9...
==========

[floitsch, 2017-05-16 12:55:53]

Committed patchset #1 (id:1) manually as
daf66909019d2aaec1721fc39d94ea648a9fdc1d (presubmit successful).