Add GlobalEscapeDirective to utils

PiperOrigin-RevId: 189299517

Author: Googler

lib/utils/keyboard/global_escape_directive.dart

@@ -0,0 +1,28 @@
+// 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.
+
+import 'dart:async';
+import 'dart:html';
+
+import 'package:angular/angular.dart';
+
+/// Directive to listen to the escape key globally.
+///
+/// Useful for things like having a dialog close when the escape key is pressed
+/// even when the dialog is not focused.
+///
+/// WARNING: If listeners to the onEscape stream are on the page but hidden,
+/// they will still be registered to the stream. To avoid that situation, use
+/// this directive only within a deferredContent directive.
+@Directive(selector: '[globalEscape]')
+class GlobalEscapeDirective {
+  final Window _window;
+
+  /// Event triggered when the escape key is pressed.
+  @Output()
+  Stream<KeyboardEvent> get globalEscape =>
+      _window.onKeyUp.where((event) => event.keyCode == KeyCode.ESC);
+
+  GlobalEscapeDirective(this._window);
+}