[Plugins] Bring over timeline, clock plugins

WTD-1239

platform/features/clock/src/services/TickerService.js

@@ -0,0 +1,68 @@
+/*global define*/
+
+define(
+    ['moment'],
+    function (moment) {
+        "use strict";
+
+        /**
+         * Calls functions every second, as close to the actual second
+         * tick as is feasible.
+         * @constructor
+         * @param $timeout Angular's $timeout
+         * @param {Function} now function to provide the current time in ms
+         */
+        function TickerService($timeout, now) {
+            var callbacks = [],
+                last = now() - 1000;
+
+            function tick() {
+                var timestamp = now(),
+                    millis = timestamp % 1000;
+
+                // Only update callbacks if a second has actually passed.
+                if (timestamp >= last + 1000) {
+                    callbacks.forEach(function (callback) {
+                        callback(timestamp);
+                    });
+                    last = timestamp - millis;
+                }
+
+                // Try to update at exactly the next second
+                $timeout(tick, 1000 - millis, true);
+            }
+
+            tick();
+
+            return {
+                /**
+                 * Listen for clock ticks. The provided callback will
+                 * be invoked with the current timestamp (in milliseconds
+                 * since Jan 1 1970) at regular intervals, as near to the
+                 * second boundary as possible.
+                 *
+                 * @method listen
+                 * @name TickerService#listen
+                 * @param {Function} callback callback to invoke
+                 * @returns {Function} a function to unregister this listener
+                 */
+                listen: function (callback) {
+                    callbacks.push(callback);
+
+                    // Provide immediate feedback
+                    callback(last);
+
+                    // Provide a deregistration function
+                    return function () {
+                        callbacks = callbacks.filter(function (cb) {
+                            return cb !== callback;
+                        });
+                    };
+                }
+            };
+
+        }
+
+        return TickerService;
+    }
+);