Add a top-level status library. R=kevmoo@google.com Review URL: https://codereview.chromium.org//1758053002 .

diff --git a/pkgs/web_socket_channel/README.md b/pkgs/web_socket_channel/README.md
index 3e984aa..2ea4408 100644
--- a/pkgs/web_socket_channel/README.md
+++ b/pkgs/web_socket_channel/README.md

@@ -11,6 +11,26 @@
 [IOWebSocketChannel]: https://www.dartdocs.org/documentation/web_socket_channel/latest/io/IOWebSocketChannel-class.html
 [HtmlWebSocketChannel]: https://www.dartdocs.org/documentation/web_socket_channel/latest/html/HtmlWebSocketChannel-class.html
 
+It also provides constants for the WebSocket protocol's pre-defined status codes
+in the [`status.dart` library][status]. It's strongly recommended that users
+import this library should be imported with the prefix `status`.
+
+[status]: https://www.dartdocs.org/documentation/web_socket_channel/latest/status/status-library.html
+
+```dart
+import 'package:web_socket_channel/io.dart';
+import 'package:web_socket_channel/status.dart' as status;
+
+main() async {
+  var channel = await IOWebSocketChannel.connect("ws://localhost:1234");
+
+  channel.stream.listen((message) {
+    channel.sink.add("received!");
+    channel.close(status.goingAway);
+  });
+}
+```
+
 ## `WebSocketChannel`
 
 The [`WebSocketChannel`][WebSocketChannel] class's most important role is as the

diff --git a/pkgs/web_socket_channel/lib/io.dart b/pkgs/web_socket_channel/lib/io.dart
index 355e250..8c225be 100644
--- a/pkgs/web_socket_channel/lib/io.dart
+++ b/pkgs/web_socket_channel/lib/io.dart

@@ -39,10 +39,10 @@
   ///
   /// [pingInterval] controls the interval for sending ping signals. If a ping
   /// message is not answered by a pong message from the peer, the WebSocket is
-  /// assumed disconnected and the connection is closed with a
-  /// [WebSocketStatus.GOING_AWAY] close code. When a ping signal is sent, the
-  /// pong message must be received within [pingInterval]. It defaults to
-  /// `null`, indicating that ping messages are disabled.
+  /// assumed disconnected and the connection is closed with a `goingAway` code.
+  /// When a ping signal is sent, the pong message must be received within
+  /// [pingInterval]. It defaults to `null`, indicating that ping messages are
+  /// disabled.
   ///
   /// If there's an error connecting, the channel's stream emits a
   /// [WebSocketChannelException] wrapping that error and then closes.

diff --git a/pkgs/web_socket_channel/lib/src/channel.dart b/pkgs/web_socket_channel/lib/src/channel.dart
index 0f640de..446eb69 100644
--- a/pkgs/web_socket_channel/lib/src/channel.dart
+++ b/pkgs/web_socket_channel/lib/src/channel.dart

@@ -80,10 +80,10 @@
   ///
   /// [pingInterval] controls the interval for sending ping signals. If a ping
   /// message is not answered by a pong message from the peer, the WebSocket is
-  /// assumed disconnected and the connection is closed with a
-  /// [WebSocketStatus.GOING_AWAY] close code. When a ping signal is sent, the
-  /// pong message must be received within [pingInterval]. It defaults to
-  /// `null`, indicating that ping messages are disabled.
+  /// assumed disconnected and the connection is closed with a `goingAway` close
+  /// code. When a ping signal is sent, the pong message must be received within
+  /// [pingInterval]. It defaults to `null`, indicating that ping messages are
+  /// disabled.
   ///
   /// If this is a WebSocket server, [serverSide] should be `true` (the
   /// default); if it's a client, [serverSide] should be `false`.

diff --git a/pkgs/web_socket_channel/lib/status.dart b/pkgs/web_socket_channel/lib/status.dart
new file mode 100644
index 0000000..8bd3f16
--- /dev/null
+++ b/pkgs/web_socket_channel/lib/status.dart

@@ -0,0 +1,88 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Status codes that are defined in the WebSocket spec.
+///
+/// This library is intended to be imported with a prefix.
+///
+/// ```dart
+/// import 'package:web_socket_channel/io.dart';
+/// import 'package:web_socket_channel/status.dart' as status;
+///
+/// main() async {
+///   var channel = await IOWebSocketChannel.connect("ws://localhost:1234");
+///   // ...
+///   channel.close(status.goingAway);
+/// }
+/// ```
+import 'dart:core';
+
+/// The purpose for which the connection was established has been fulfilled.
+const normalClosure = 1000;
+
+/// An endpoint is "going away", such as a server going down or a browser having
+/// navigated away from a page.
+const goingAway = 1001;
+
+/// An endpoint is terminating the connection due to a protocol error.
+const protocolError = 1002;
+
+/// An endpoint is terminating the connection because it has received a type of
+/// data it cannot accept.
+///
+/// For example, an endpoint that understands only text data MAY send this if it
+/// receives a binary message).
+const unsupportedData = 1003;
+
+/// No status code was present.
+///
+/// This **must not** be set explicitly by an endpoint.
+const noStatusReceived = 1005;
+
+/// The connection was closed abnormally.
+///
+/// For example, this is used if the connection was closed without sending or
+/// receiving a Close control frame.
+///
+/// This **must not** be set explicitly by an endpoint.
+const abnormalClosure = 1006;
+
+/// An endpoint is terminating the connection because it has received data
+/// within a message that was not consistent with the type of the message.
+///
+/// For example, the endpoint may have receieved non-UTF-8 data within a text
+/// message.
+const invalidFramePayloadData = 1007;
+
+/// An endpoint is terminating the connection because it has received a message
+/// that violates its policy.
+///
+/// This is a generic status code that can be returned when there is no other
+/// more suitable status code (such as [unsupportedData] or [messageTooBig]), or
+/// if there is a need to hide specific details about the policy.
+const policyViolation = 1008;
+
+/// An endpoint is terminating the connection because it has received a message
+/// that is too big for it to process.
+const messageTooBig = 1009;
+
+/// The client is terminating the connection because it expected the server to
+/// negotiate one or more extensions, but the server didn't return them in the
+/// response message of the WebSocket handshake.
+///
+/// The list of extensions that are needed should appear in the close reason.
+/// Note that this status code is not used by the server, because it can fail
+/// the WebSocket handshake instead.
+const missingMandatoryExtension = 1010;
+
+/// The server is terminating the connection because it encountered an
+/// unexpected condition that prevented it from fulfilling the request.
+const internalServerError = 1011;
+
+/// The connection was closed due to a failure to perform a TLS handshake.
+///
+/// For example, the server certificate may not have been verified.
+///
+/// This **must not** be set explicitly by an endpoint.
+const tlsHandshakeFailed = 1015;

diff --git a/pkgs/web_socket_channel/pubspec.yaml b/pkgs/web_socket_channel/pubspec.yaml
index c6ad187..2888da6 100644
--- a/pkgs/web_socket_channel/pubspec.yaml
+++ b/pkgs/web_socket_channel/pubspec.yaml

@@ -1,5 +1,5 @@
 name: web_socket_channel
-version: 1.0.0-dev
+version: 1.0.0
 description: StreamChannel wrappers for WebSockets.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/web_socket_channel