void
nsAnimationManager::FlushAnimations(FlushFlags aFlags)
{
  // FIXME: check that there's at least one style rule that's not
  // in its "done" state, and if there isn't, remove ourselves from
  // the refresh driver (but leave the animations!).
  TimeStamp now = mPresContext->RefreshDriver()->MostRecentRefresh();
  bool didThrottle = false;
  for (PRCList *l = PR_LIST_HEAD(&mElementCollections);
       l != &mElementCollections;
       l = PR_NEXT_LINK(l)) {
    AnimationPlayerCollection* collection =
      static_cast<AnimationPlayerCollection*>(l);

    nsAutoAnimationMutationBatch mb(collection->mElement);

    collection->Tick();
    bool canThrottleTick = aFlags == Can_Throttle &&
      collection->CanPerformOnCompositorThread(
        AnimationPlayerCollection::CanAnimateFlags(0)) &&
      collection->CanThrottleAnimation(now);

    nsRefPtr<css::AnimValuesStyleRule> oldStyleRule = collection->mStyleRule;
    UpdateStyleAndEvents(collection, now, canThrottleTick
                                          ? EnsureStyleRule_IsThrottled
                                          : EnsureStyleRule_IsNotThrottled);
    if (oldStyleRule != collection->mStyleRule) {
      collection->PostRestyleForAnimation(mPresContext);
    } else {
      didThrottle = true;
    }
  }

  if (didThrottle) {
    mPresContext->Document()->SetNeedStyleFlush();
  }

  DispatchEvents(); // may destroy us
}
nsIStyleRule*
nsAnimationManager::CheckAnimationRule(nsStyleContext* aStyleContext,
                                       mozilla::dom::Element* aElement)
{
  // FIXME (bug 960465): This test should go away.
  if (!mPresContext->RestyleManager()->IsProcessingAnimationStyleChange()) {
    if (!mPresContext->IsDynamic()) {
      // For print or print preview, ignore animations.
      return nullptr;
    }

    // Everything that causes our animation data to change triggers a
    // style change, which in turn triggers a non-animation restyle.
    // Likewise, when we initially construct frames, we're not in a
    // style change, but also not in an animation restyle.

    const nsStyleDisplay* disp = aStyleContext->StyleDisplay();
    AnimationPlayerCollection* collection =
      GetAnimationPlayers(aElement, aStyleContext->GetPseudoType(), false);
    if (!collection &&
        disp->mAnimationNameCount == 1 &&
        disp->mAnimations[0].GetName().IsEmpty()) {
      return nullptr;
    }

    // build the animations list
    dom::AnimationTimeline* timeline = aElement->OwnerDoc()->Timeline();
    AnimationPlayerPtrArray newPlayers;
    BuildAnimations(aStyleContext, aElement, timeline, newPlayers);

    if (newPlayers.IsEmpty()) {
      if (collection) {
        collection->Destroy();
      }
      return nullptr;
    }

    if (collection) {
      collection->mStyleRule = nullptr;
      collection->mStyleRuleRefreshTime = TimeStamp();
      collection->UpdateAnimationGeneration(mPresContext);

      // Copy over the start times and (if still paused) pause starts
      // for each animation (matching on name only) that was also in the
      // old list of animations.
      // This means that we honor dynamic changes, which isn't what the
      // spec says to do, but WebKit seems to honor at least some of
      // them.  See
      // http://lists.w3.org/Archives/Public/www-style/2011Apr/0079.html
      // In order to honor what the spec said, we'd copy more data over
      // (or potentially optimize BuildAnimations to avoid rebuilding it
      // in the first place).
      if (!collection->mPlayers.IsEmpty()) {

        for (size_t newIdx = newPlayers.Length(); newIdx-- != 0;) {
          AnimationPlayer* newPlayer = newPlayers[newIdx];

          // Find the matching animation with this name in the old list
          // of animations.  We iterate through both lists in a backwards
          // direction which means that if there are more animations in
          // the new list of animations with a given name than in the old
          // list, it will be the animations towards the of the beginning of
          // the list that do not match and are treated as new animations.
          nsRefPtr<CSSAnimationPlayer> oldPlayer;
          size_t oldIdx = collection->mPlayers.Length();
          while (oldIdx-- != 0) {
            CSSAnimationPlayer* a =
              collection->mPlayers[oldIdx]->AsCSSAnimationPlayer();
            MOZ_ASSERT(a, "All players in the CSS Animation collection should"
                          " be CSSAnimationPlayer objects");
            if (a->Name() == newPlayer->Name()) {
              oldPlayer = a;
              break;
            }
          }
          if (!oldPlayer) {
            continue;
          }

          // Update the old from the new so we can keep the original object
          // identity (and any expando properties attached to it).
          if (oldPlayer->GetSource() && newPlayer->GetSource()) {
            Animation* oldAnim = oldPlayer->GetSource();
            Animation* newAnim = newPlayer->GetSource();
            oldAnim->Timing() = newAnim->Timing();
            oldAnim->Properties() = newAnim->Properties();
          }

          // Reset compositor state so animation will be re-synchronized.
          oldPlayer->ClearIsRunningOnCompositor();

          // Handle changes in play state.
          // CSSAnimationPlayer takes care of override behavior so that,
          // for example, if the author has called pause(), that will
          // override the animation-play-state.
          // (We should check newPlayer->IsStylePaused() but that requires
          //  downcasting to CSSAnimationPlayer and we happen to know that
          //  newPlayer will only ever be paused by calling PauseFromStyle
          //  making IsPaused synonymous in this case.)
          if (!oldPlayer->IsStylePaused() && newPlayer->IsPaused()) {
            oldPlayer->PauseFromStyle();
          } else if (oldPlayer->IsStylePaused() && !newPlayer->IsPaused()) {
            oldPlayer->PlayFromStyle();
          }

          // Replace new animation with the (updated) old one and remove the
          // old one from the array so we don't try to match it any more.
          //
          // Although we're doing this while iterating this is safe because
          // we're not changing the length of newPlayers and we've finished
          // iterating over the list of old iterations.
          newPlayer = nullptr;
          newPlayers.ReplaceElementAt(newIdx, oldPlayer);
          collection->mPlayers.RemoveElementAt(oldIdx);
        }
      }
    } else {
      collection =
        GetAnimationPlayers(aElement, aStyleContext->GetPseudoType(), true);
    }
    collection->mPlayers.SwapElements(newPlayers);
    collection->mNeedsRefreshes = true;
    collection->Tick();

    TimeStamp refreshTime = mPresContext->RefreshDriver()->MostRecentRefresh();
    UpdateStyleAndEvents(collection, refreshTime,
                         EnsureStyleRule_IsNotThrottled);
    // We don't actually dispatch the mPendingEvents now.  We'll either
    // dispatch them the next time we get a refresh driver notification
    // or the next time somebody calls
    // nsPresShell::FlushPendingNotifications.
    if (!mPendingEvents.IsEmpty()) {
      mPresContext->Document()->SetNeedStyleFlush();
    }
  }

  return GetAnimationRule(aElement, aStyleContext->GetPseudoType());
}