DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (c291143e2401)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

/**
 * Set of actors that expose the Web Animations API to devtools protocol
 * clients.
 *
 * The |Animations| actor is the main entry point. It is used to discover
 * animation players on given nodes.
 * There should only be one instance per debugger server.
 *
 * The |AnimationPlayer| actor provides attributes and methods to inspect an
 * animation as well as pause/resume/seek it.
 *
 * The Web Animation spec implementation is ongoing in Gecko, and so this set
 * of actors should evolve when the implementation progresses.
 *
 * References:
 * - WebAnimation spec:
 *   http://drafts.csswg.org/web-animations/
 * - WebAnimation WebIDL files:
 *   /dom/webidl/Animation*.webidl
 */

const {Cu} = require("chrome");
const protocol = require("devtools/shared/protocol");
const {Actor} = protocol;
const {animationPlayerSpec, animationsSpec} = require("devtools/shared/specs/animation");
const {ANIMATION_TYPE_FOR_LONGHANDS} = require("./animation-type-longhand");

// Types of animations.
const ANIMATION_TYPES = {
  CSS_ANIMATION: "cssanimation",
  CSS_TRANSITION: "csstransition",
  SCRIPT_ANIMATION: "scriptanimation",
  UNKNOWN: "unknown"
};
exports.ANIMATION_TYPES = ANIMATION_TYPES;

function getAnimationTypeForLonghand(property) {
  for (const [type, props] of ANIMATION_TYPE_FOR_LONGHANDS) {
    if (props.has(property)) {
      return type;
    }
  }
  throw new Error("Unknown longhand property name");
}
exports.getAnimationTypeForLonghand = getAnimationTypeForLonghand;

/**
 * The AnimationPlayerActor provides information about a given animation: its
 * startTime, currentTime, current state, etc.
 *
 * Since the state of a player changes as the animation progresses it is often
 * useful to call getCurrentState at regular intervals to get the current state.
 *
 * This actor also allows playing, pausing and seeking the animation.
 */
var AnimationPlayerActor = protocol.ActorClassWithSpec(animationPlayerSpec, {
  /**
   * @param {AnimationsActor} The main AnimationsActor instance
   * @param {AnimationPlayer} The player object returned by getAnimationPlayers
   * @param {Number} Time which animation created
   */
  initialize: function(animationsActor, player, createdTime) {
    Actor.prototype.initialize.call(this, animationsActor.conn);

    this.onAnimationMutation = this.onAnimationMutation.bind(this);

    this.walker = animationsActor.walker;
    this.player = player;

    // Listen to animation mutations on the node to alert the front when the
    // current animation changes.
    // If the node is a pseudo-element, then we listen on its parent with
    // subtree:true (there's no risk of getting too many notifications in
    // onAnimationMutation since we filter out events that aren't for the
    // current animation).
    this.observer = new this.window.MutationObserver(this.onAnimationMutation);
    if (this.isPseudoElement) {
      this.observer.observe(this.node.parentElement,
                            {animations: true, subtree: true});
    } else {
      this.observer.observe(this.node, {animations: true});
    }

    this.createdTime = createdTime;
    this.currentTimeAtCreated = player.currentTime;
  },

  destroy: function() {
    // Only try to disconnect the observer if it's not already dead (i.e. if the
    // container view hasn't navigated since).
    if (this.observer && !Cu.isDeadWrapper(this.observer)) {
      this.observer.disconnect();
    }
    this.player = this.observer = this.walker = null;

    Actor.prototype.destroy.call(this);
  },

  get isPseudoElement() {
    return !this.player.effect.target.ownerDocument;
  },

  get node() {
    if (!this.isPseudoElement) {
      return this.player.effect.target;
    }

    const pseudo = this.player.effect.target;
    const treeWalker = this.walker.getDocumentWalker(pseudo.parentElement);
    return pseudo.type === "::before" ? treeWalker.firstChild() : treeWalker.lastChild();
  },

  get document() {
    return this.node.ownerDocument;
  },

  get window() {
    return this.document.defaultView;
  },

  /**
   * Release the actor, when it isn't needed anymore.
   * Protocol.js uses this release method to call the destroy method.
   */
  release: function() {},

  form: function(detail) {
    if (detail === "actorid") {
      return this.actorID;
    }

    const data = this.getCurrentState();
    data.actor = this.actorID;

    // If we know the WalkerActor, and if the animated node is known by it, then
    // return its corresponding NodeActor ID too.
    if (this.walker && this.walker.hasNode(this.node)) {
      data.animationTargetNodeActorID = this.walker.getNode(this.node).actorID;
    }

    return data;
  },

  isCssAnimation: function(player = this.player) {
    return player instanceof this.window.CSSAnimation;
  },

  isCssTransition: function(player = this.player) {
    return player instanceof this.window.CSSTransition;
  },

  isScriptAnimation: function(player = this.player) {
    return player instanceof this.window.Animation && !(
      player instanceof this.window.CSSAnimation ||
      player instanceof this.window.CSSTransition
    );
  },

  getType: function() {
    if (this.isCssAnimation()) {
      return ANIMATION_TYPES.CSS_ANIMATION;
    } else if (this.isCssTransition()) {
      return ANIMATION_TYPES.CSS_TRANSITION;
    } else if (this.isScriptAnimation()) {
      return ANIMATION_TYPES.SCRIPT_ANIMATION;
    }

    return ANIMATION_TYPES.UNKNOWN;
  },

  /**
   * Get the name of this animation. This can be either the animation.id
   * property if it was set, or the keyframe rule name or the transition
   * property.
   * @return {String}
   */
  getName: function() {
    if (this.player.id) {
      return this.player.id;
    } else if (this.isCssAnimation()) {
      return this.player.animationName;
    } else if (this.isCssTransition()) {
      return this.player.transitionProperty;
    }

    return "";
  },

  /**
   * Get the animation duration from this player, in milliseconds.
   * @return {Number}
   */
  getDuration: function() {
    return this.player.effect.getComputedTiming().duration;
  },

  /**
   * Get the animation delay from this player, in milliseconds.
   * @return {Number}
   */
  getDelay: function() {
    return this.player.effect.getComputedTiming().delay;
  },

  /**
   * Get the animation endDelay from this player, in milliseconds.
   * @return {Number}
   */
  getEndDelay: function() {
    return this.player.effect.getComputedTiming().endDelay;
  },

  /**
   * Get the animation iteration count for this player. That is, how many times
   * is the animation scheduled to run.
   * @return {Number} The number of iterations, or null if the animation repeats
   * infinitely.
   */
  getIterationCount: function() {
    const iterations = this.player.effect.getComputedTiming().iterations;
    return iterations === Infinity ? null : iterations;
  },

  /**
   * Get the animation iterationStart from this player, in ratio.
   * That is offset of starting position of the animation.
   * @return {Number}
   */
  getIterationStart: function() {
    return this.player.effect.getComputedTiming().iterationStart;
  },

  /**
   * Get the animation easing from this player.
   * @return {String}
   */
  getEasing: function() {
    return this.player.effect.getComputedTiming().easing;
  },

  /**
   * Get the animation fill mode from this player.
   * @return {String}
   */
  getFill: function() {
    return this.player.effect.getComputedTiming().fill;
  },

  /**
   * Get the animation direction from this player.
   * @return {String}
   */
  getDirection: function() {
    return this.player.effect.getComputedTiming().direction;
  },

  /**
   * Get animation-timing-function from animated element if CSS Animations.
   * @return {String}
   */
  getAnimationTimingFunction: function() {
    if (!this.isCssAnimation()) {
      return null;
    }

    let pseudo = null;
    let target = this.player.effect.target;
    if (target.type) {
      // Animated element is a pseudo element.
      pseudo = target.type;
      target = target.parentElement;
    }
    return this.window.getComputedStyle(target, pseudo).animationTimingFunction;
  },

  getPropertiesCompositorStatus: function() {
    const properties = this.player.effect.getProperties();
    return properties.map(prop => {
      return {
        property: prop.property,
        runningOnCompositor: prop.runningOnCompositor,
        warning: prop.warning
      };
    });
  },

  /**
   * Return the current start of the Animation.
   * @return {Object}
   */
  getState: function() {
    // Note that if you add a new property to the state object, make sure you
    // add the corresponding property in the AnimationPlayerFront' initialState
    // getter.
    return {
      type: this.getType(),
      // startTime is null whenever the animation is paused or waiting to start.
      startTime: this.player.startTime,
      currentTime: this.player.currentTime,
      playState: this.player.playState,
      playbackRate: this.player.playbackRate,
      name: this.getName(),
      duration: this.getDuration(),
      delay: this.getDelay(),
      endDelay: this.getEndDelay(),
      iterationCount: this.getIterationCount(),
      iterationStart: this.getIterationStart(),
      fill: this.getFill(),
      easing: this.getEasing(),
      direction: this.getDirection(),
      animationTimingFunction: this.getAnimationTimingFunction(),
      // animation is hitting the fast path or not. Returns false whenever the
      // animation is paused as it is taken off the compositor then.
      isRunningOnCompositor:
        this.getPropertiesCompositorStatus()
            .some(propState => propState.runningOnCompositor),
      propertyState: this.getPropertiesCompositorStatus(),
      // The document timeline's currentTime is being sent along too. This is
      // not strictly related to the node's animationPlayer, but is useful to
      // know the current time of the animation with respect to the document's.
      documentCurrentTime: this.node.ownerDocument.timeline.currentTime,
      // The time which this animation created.
      createdTime: this.createdTime,
      // The time which an animation's current time when this animation has created.
      currentTimeAtCreated: this.currentTimeAtCreated,
    };
  },

  /**
   * Get the current state of the AnimationPlayer (currentTime, playState, ...).
   * Note that the initial state is returned as the form of this actor when it
   * is initialized.
   * This protocol method only returns a trimed down version of this state in
   * case some properties haven't changed since last time (since the front can
   * reconstruct those). If you want the full state, use the getState method.
   * @return {Object}
   */
  getCurrentState: function() {
    const newState = this.getState();

    // If we've saved a state before, compare and only send what has changed.
    // It's expected of the front to also save old states to re-construct the
    // full state when an incomplete one is received.
    // This is to minimize protocol traffic.
    let sentState = {};
    if (this.currentState) {
      for (const key in newState) {
        if (typeof this.currentState[key] === "undefined" ||
            this.currentState[key] !== newState[key]) {
          sentState[key] = newState[key];
        }
      }
    } else {
      sentState = newState;
    }
    this.currentState = newState;

    return sentState;
  },

  /**
   * Executed when the current animation changes, used to emit the new state
   * the the front.
   */
  onAnimationMutation: function(mutations) {
    const isCurrentAnimation = animation => animation === this.player;
    const hasCurrentAnimation = animations => animations.some(isCurrentAnimation);
    let hasChanged = false;

    for (const {removedAnimations, changedAnimations} of mutations) {
      if (hasCurrentAnimation(removedAnimations)) {
        // Reset the local copy of the state on removal, since the animation can
        // be kept on the client and re-added, its state needs to be sent in
        // full.
        this.currentState = null;
      }

      if (hasCurrentAnimation(changedAnimations)) {
        // Only consider the state has having changed if any of effect timing properties,
        // animationTimingFunction or playbackRate has changed.
        const newState = this.getState();
        const oldState = this.currentState;
        hasChanged = newState.delay !== oldState.delay ||
                     newState.iterationCount !== oldState.iterationCount ||
                     newState.iterationStart !== oldState.iterationStart ||
                     newState.duration !== oldState.duration ||
                     newState.endDelay !== oldState.endDelay ||
                     newState.direction !== oldState.direction ||
                     newState.easing !== oldState.easing ||
                     newState.fill !== oldState.fill ||
                     newState.animationTimingFunction !==
                       oldState.animationTimingFunction ||
                     newState.playbackRate !== oldState.playbackRate;
        break;
      }
    }

    if (hasChanged) {
      this.emit("changed", this.getCurrentState());
    }
  },

  /**
   * Get data about the animated properties of this animation player.
   * @return {Array} Returns a list of animated properties.
   * Each property contains a list of values, their offsets and distances.
   */
  getProperties: function() {
    const properties = this.player.effect.getProperties().map(property => {
      return {name: property.property, values: property.values};
    });

    const DOMWindowUtils = this.window.windowUtils;

    // Fill missing keyframe with computed value.
    for (const property of properties) {
      let underlyingValue = null;
      // Check only 0% and 100% keyframes.
      [0, property.values.length - 1].forEach(index => {
        const values = property.values[index];
        if (values.value !== undefined) {
          return;
        }
        if (!underlyingValue) {
          let pseudo = null;
          let target = this.player.effect.target;
          if (target.type) {
            // This target is a pseudo element.
            pseudo = target.type;
            target = target.parentElement;
          }
          const value =
            DOMWindowUtils.getUnanimatedComputedStyle(target,
                                                      pseudo,
                                                      property.name,
                                                      DOMWindowUtils.FLUSH_NONE);
          const animationType = getAnimationTypeForLonghand(property.name);
          underlyingValue = animationType === "float" ? parseFloat(value, 10) : value;
        }
        values.value = underlyingValue;
      });
    }

    // Calculate the distance.
    for (const property of properties) {
      const propertyName = property.name;
      const maxObject = { distance: -1 };
      for (let i = 0; i < property.values.length - 1; i++) {
        const value1 = property.values[i].value;
        for (let j = i + 1; j < property.values.length; j++) {
          const value2 = property.values[j].value;
          const distance =
            this.getDistance(this.node, propertyName, value1, value2, DOMWindowUtils);
          if (maxObject.distance >= distance) {
            continue;
          }
          maxObject.distance = distance;
          maxObject.value1 = value1;
          maxObject.value2 = value2;
        }
      }
      if (maxObject.distance === 0) {
        // Distance is zero means that no values change or can't calculate the distance.
        // In this case, we use the keyframe offset as the distance.
        property.values.reduce((previous, current) => {
          // If the current value is same as previous value, use previous distance.
          current.distance =
            current.value === previous.value ? previous.distance : current.offset;
          return current;
        }, property.values[0]);
        continue;
      }
      const baseValue =
        maxObject.value1 < maxObject.value2 ? maxObject.value1 : maxObject.value2;
      for (const values of property.values) {
        const value = values.value;
        const distance =
          this.getDistance(this.node, propertyName, baseValue, value, DOMWindowUtils);
        values.distance = distance / maxObject.distance;
      }
    }
    return properties;
  },

  /**
   * Get the animation types for a given list of CSS property names.
   * @param {Array} propertyNames - CSS property names (e.g. background-color)
   * @return {Object} Returns animation types (e.g. {"background-color": "rgb(0, 0, 0)"}.
   */
  getAnimationTypes: function(propertyNames) {
    const animationTypes = {};
    for (const propertyName of propertyNames) {
      animationTypes[propertyName] = getAnimationTypeForLonghand(propertyName);
    }
    return animationTypes;
  },

  /**
   * Returns the distance of between value1, value2.
   * @param {Object} target - dom element
   * @param {String} propertyName - e.g. transform
   * @param {String} value1 - e.g. translate(0px)
   * @param {String} value2 - e.g. translate(10px)
   * @param {Object} DOMWindowUtils
   * @param {float} distance
   */
  getDistance: function(target, propertyName, value1, value2, DOMWindowUtils) {
    if (value1 === value2) {
      return 0;
    }
    try {
      const distance =
        DOMWindowUtils.computeAnimationDistance(target, propertyName, value1, value2);
      return distance;
    } catch (e) {
      // We can't compute the distance such the 'discrete' animation,
      // 'auto' keyword and so on.
      return 0;
    }
  }
});

exports.AnimationPlayerActor = AnimationPlayerActor;

/**
 * The Animations actor lists animation players for a given node.
 */
exports.AnimationsActor = protocol.ActorClassWithSpec(animationsSpec, {
  initialize: function(conn, targetActor) {
    Actor.prototype.initialize.call(this, conn);
    this.targetActor = targetActor;

    this.onWillNavigate = this.onWillNavigate.bind(this);
    this.onNavigate = this.onNavigate.bind(this);
    this.onAnimationMutation = this.onAnimationMutation.bind(this);

    this.allAnimationsPaused = false;
    this.targetActor.on("will-navigate", this.onWillNavigate);
    this.targetActor.on("navigate", this.onNavigate);
  },

  destroy: function() {
    Actor.prototype.destroy.call(this);
    this.targetActor.off("will-navigate", this.onWillNavigate);
    this.targetActor.off("navigate", this.onNavigate);

    this.stopAnimationPlayerUpdates();
    this.targetActor = this.observer = this.actors = this.walker = null;
  },

  /**
   * Clients can optionally call this with a reference to their WalkerActor.
   * If they do, then AnimationPlayerActor's forms are going to also include
   * NodeActor IDs when the corresponding NodeActors do exist.
   * This, in turns, is helpful for clients to avoid having to go back once more
   * to the server to get a NodeActor for a particular animation.
   * @param {WalkerActor} walker
   */
  setWalkerActor: function(walker) {
    this.walker = walker;
  },

  /**
   * Retrieve the list of AnimationPlayerActor actors for currently running
   * animations on a node and its descendants.
   * Note that calling this method a second time will destroy all previously
   * retrieved AnimationPlayerActors. Indeed, the lifecycle of these actors
   * is managed here on the server and tied to getAnimationPlayersForNode
   * being called.
   * @param {NodeActor} nodeActor The NodeActor as defined in
   * /devtools/server/actors/inspector
   */
  getAnimationPlayersForNode: function(nodeActor) {
    const animations = nodeActor.rawNode.getAnimations({subtree: true});

    // Destroy previously stored actors
    if (this.actors) {
      for (const actor of this.actors) {
        actor.destroy();
      }
    }

    this.actors = [];

    for (const animation of animations) {
      const createdTime = this.getCreatedTime(animation);
      const actor = AnimationPlayerActor(this, animation, createdTime);
      this.actors.push(actor);
    }

    // When a front requests the list of players for a node, start listening
    // for animation mutations on this node to send updates to the front, until
    // either getAnimationPlayersForNode is called again or
    // stopAnimationPlayerUpdates is called.
    this.stopAnimationPlayerUpdates();
    // ownerGlobal doesn't exist in content privileged windows.
    // eslint-disable-next-line mozilla/use-ownerGlobal
    const win = nodeActor.rawNode.ownerDocument.defaultView;
    this.observer = new win.MutationObserver(this.onAnimationMutation);
    this.observer.observe(nodeActor.rawNode, {
      animations: true,
      subtree: true
    });

    return this.actors;
  },

  onAnimationMutation: function(mutations) {
    const eventData = [];
    const readyPromises = [];

    for (const {addedAnimations, removedAnimations} of mutations) {
      for (const player of removedAnimations) {
        // Note that animations are reported as removed either when they are
        // actually removed from the node (e.g. css class removed) or when they
        // are finished and don't have forwards animation-fill-mode.
        // In the latter case, we don't send an event, because the corresponding
        // animation can still be seeked/resumed, so we want the client to keep
        // its reference to the AnimationPlayerActor.
        if (player.playState !== "idle") {
          continue;
        }

        const index = this.actors.findIndex(a => a.player === player);
        if (index !== -1) {
          eventData.push({
            type: "removed",
            player: this.actors[index]
          });
          this.actors.splice(index, 1);
        }
      }

      for (const player of addedAnimations) {
        // If the added player already exists, it means we previously filtered
        // it out when it was reported as removed. So filter it out here too.
        if (this.actors.find(a => a.player === player)) {
          continue;
        }

        // If the added player has the same name and target node as a player we
        // already have, it means it's a transition that's re-starting. So send
        // a "removed" event for the one we already have.
        const index = this.actors.findIndex(a => {
          const isSameType = a.player.constructor === player.constructor;
          const isSameName = (a.isCssAnimation() &&
                            a.player.animationName === player.animationName) ||
                           (a.isCssTransition() &&
                            a.player.transitionProperty === player.transitionProperty);
          const isSameNode = a.player.effect.target === player.effect.target;

          return isSameType && isSameNode && isSameName;
        });
        if (index !== -1) {
          eventData.push({
            type: "removed",
            player: this.actors[index]
          });
          this.actors.splice(index, 1);
        }

        const createdTime = this.getCreatedTime(player);
        const actor = AnimationPlayerActor(this, player, createdTime);
        this.actors.push(actor);
        eventData.push({
          type: "added",
          player: actor
        });
        readyPromises.push(player.ready);
      }
    }

    if (eventData.length) {
      // Let's wait for all added animations to be ready before telling the
      // front-end.
      Promise.all(readyPromises).then(() => {
        this.emit("mutations", eventData);
      });
    }
  },

  /**
   * After the client has called getAnimationPlayersForNode for a given DOM
   * node, the actor starts sending animation mutations for this node. If the
   * client doesn't want this to happen anymore, it should call this method.
   */
  stopAnimationPlayerUpdates: function() {
    if (this.observer && !Cu.isDeadWrapper(this.observer)) {
      this.observer.disconnect();
    }
  },

  /**
   * Iterates through all nodes below a given rootNode (optionally also in
   * nested frames) and finds all existing animation players.
   * @param {DOMNode} rootNode The root node to start iterating at. Animation
   * players will *not* be reported for this node.
   * @param {Boolean} traverseFrames Whether we should iterate through nested
   * frames too.
   * @return {Array} An array of AnimationPlayer objects.
   */
  getAllAnimations: function(rootNode, traverseFrames) {
    if (!traverseFrames) {
      return rootNode.getAnimations({subtree: true});
    }

    let animations = [];
    for (const {document} of this.targetActor.windows) {
      animations = [...animations, ...document.getAnimations({subtree: true})];
    }
    return animations;
  },

  onWillNavigate: function({isTopLevel}) {
    if (isTopLevel) {
      this.stopAnimationPlayerUpdates();
    }
  },

  onNavigate: function({isTopLevel}) {
    if (isTopLevel) {
      this.allAnimationsPaused = false;
    }
  },

  /**
   * Pause given animations.
   *
   * @param {Array} actors A list of AnimationPlayerActor.
   */
  pauseSome: function(actors) {
    for (const { player } of actors) {
      this.pauseSync(player);
    }

    return this.waitForNextFrame(actors);
  },

  /**
   * Play given animations.
   *
   * @param {Array} actors A list of AnimationPlayerActor.
   */
  playSome: function(actors) {
    for (const { player } of actors) {
      this.playSync(player);
    }

    return this.waitForNextFrame(actors);
  },

  /**
   * Set the current time of several animations at the same time.
   * @param {Array} players A list of AnimationPlayerActor.
   * @param {Number} time The new currentTime.
   * @param {Boolean} shouldPause Should the players be paused too.
   */
  setCurrentTimes: function(players, time, shouldPause) {
    for (const actor of players) {
      const player = actor.player;

      if (shouldPause) {
        player.startTime = null;
      }

      player.currentTime = (time - actor.createdTime) * player.playbackRate;
    }

    return this.waitForNextFrame(players);
  },

  /**
   * Set the playback rate of several animations at the same time.
   * @param {Array} actors A list of AnimationPlayerActor.
   * @param {Number} rate The new rate.
   */
  setPlaybackRates: function(players, rate) {
    return Promise.all(players.map(({ player }) => {
      player.updatePlaybackRate(rate);
      return player.ready;
    }));
  },

  /**
   * Pause given player synchronously.
   *
   * @param {Object} player
   */
  pauseSync(player) {
    player.startTime = null;
  },

  /**
   * Play given player synchronously.
   *
   * @param {Object} player
   */
  playSync(player) {
    if (!player.playbackRate) {
      // We can not play with playbackRate zero.
      return;
    }

    // Play animation in a synchronous fashion by setting the start time directly.
    const currentTime = player.currentTime || 0;
    player.startTime = player.timeline.currentTime - currentTime / player.playbackRate;
  },

  /**
   * Return created fime of given animaiton.
   *
   * @param {Object} animation
   */
  getCreatedTime(animation) {
    return animation.startTime ||
          animation.timeline.currentTime - animation.currentTime / animation.playbackRate;
  },

  /**
   * Wait for next animation frame.
   *
   * @param {Array} actors
   * @return {Promise} which waits for next frame
   */
  waitForNextFrame(actors) {
    const promises = actors.map(actor => {
      const doc = actor.document;
      const win = actor.window;
      const timeAtCurrent = doc.timeline.currentTime;

      return new Promise(resolve => {
        win.requestAnimationFrame(() => {
          if (timeAtCurrent === doc.timeline.currentTime) {
            win.requestAnimationFrame(resolve);
          } else {
            resolve();
          }
        });
      });
    });

    return Promise.all(promises);
  },
});