Rolling forward https://codereview.chromium.org/1155683008/ which was

third_party/polymer/v0_8/components-chromium/neon-animation/neon-animation-runner-behavior-extracted.js

-
-
-  /**
-   * `Polymer.NeonAnimationRunnerBehavior` adds a method to run animations.
-   * @polymerBehavior
-   */
-  Polymer.NeonAnimationRunnerBehavior = [Polymer.NeonAnimatableBehavior, {
-
-    properties: {
-
-      _animationMeta: {
-        type: Object,
-        value: function() {
-          return new Polymer.IronMeta({type: 'animation'});
-        }
-      },
-
-      _player: {
-        type: Object
-      }
-
-    },
-
-    _configureAnimationEffects: function(allConfigs) {
-      var allAnimations = [];
-      if (allConfigs.length > 0) {
-        for (var config, index = 0; config = allConfigs[index]; index++) {
-          var animationConstructor = this._animationMeta.byKey(config.name);
-          if (animationConstructor) {
-            var animation = animationConstructor && new animationConstructor();
-            var effect = animation.configure(config);
-            if (effect) {
-              allAnimations.push({
-                animation: animation,
-                config: config,
-                effect: effect
-              });
-            }
-          } else {
-            console.warn(this.is + ':', config.name, 'not found!');
-          }
-        }
-      }
-      return allAnimations;
-    },
-
-    _runAnimationEffects: function(allEffects) {
-      return player = document.timeline.play(new GroupEffect(allEffects));
-    },
-
-    _completeAnimations: function(allAnimations) {
-      for (var animation, index = 0; animation = allAnimations[index]; index++) {
-        animation.animation.complete(animation.config);
-      }
-    },
-
-    /**
-     * Plays an animation with an optional `type`.
-     */
-    playAnimation: function(type, cookie) {
-      var allConfigs = this.getAnimationConfig(type);
-      if (!allConfigs) {
-        return;
-      }
-      var allAnimations = this._configureAnimationEffects(allConfigs);
-      var allEffects = allAnimations.map(function(animation) {
-        return animation.effect;
-      });
-
-      if (allEffects.length > 0) {
-        this._player = this._runAnimationEffects(allEffects);
-        this._player.onfinish = function() {
-          this._completeAnimations(allAnimations);
-
-          if (this._player) {
-            this._player.cancel();
-            this._player = null;
-          }
-
-          this.fire('neon-animation-finish', cookie, {bubbles: false});
-        }.bind(this);
-
-      } else {
-        this.fire('neon-animation-finish', cookie, {bubbles: false});
-      }
-    },
-
-    /**
-     * Cancels the currently running animation.
-     */
-    cancelAnimation: function() {
-      if (this._player) {
-        this._player.cancel();
-      }
-    }
-
-  }];