Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/contextual/js/views/KeyboardView.js

@@ -0,0 +1,61 @@
+/**
+ * @file
+ * A Backbone View that provides keyboard interaction for a contextual link.
+ */
+
+(function (Drupal, Backbone) {
+
+  "use strict";
+
+  Drupal.contextual.KeyboardView = Backbone.View.extend(/** @lends Drupal.contextual.KeyboardView# */{
+
+    /**
+     * @type {object}
+     */
+    events: {
+      'focus .trigger': 'focus',
+      'focus .contextual-links a': 'focus',
+      'blur .trigger': function () { this.model.blur(); },
+      'blur .contextual-links a': function () {
+        // Set up a timeout to allow a user to tab between the trigger and the
+        // contextual links without the menu dismissing.
+        var that = this;
+        this.timer = window.setTimeout(function () {
+          that.model.close().blur();
+        }, 150);
+      }
+    },
+
+    /**
+     * Provides keyboard interaction for a contextual link.
+     *
+     * @constructs
+     *
+     * @augments Backbone.View
+     */
+    initialize: function () {
+
+      /**
+       * The timer is used to create a delay before dismissing the contextual
+       * links on blur. This is only necessary when keyboard users tab into
+       * contextual links without edit mode (i.e. without TabbingManager).
+       * That means that if we decide to disable tabbing of contextual links
+       * without edit mode, all this timer logic can go away.
+       *
+       * @type {NaN|number}
+       */
+      this.timer = NaN;
+    },
+
+    /**
+     * Sets focus on the model; Clears the timer that dismisses the links.
+     */
+    focus: function () {
+      // Clear the timeout that might have been set by blurring a link.
+      window.clearTimeout(this.timer);
+      this.model.focus();
+    }
+
+  });
+
+})(Drupal, Backbone);