new file mode 100644
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+++ b/mobile/android/base/java/org/mozilla/gecko/widget/DefaultItemAnimatorBase.java
@@ -0,0 +1,685 @@
+/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
+ * 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/. */
+
+package org.mozilla.gecko.widget;
+
+import android.support.annotation.NonNull;
+import android.support.v4.animation.AnimatorCompatHelper;
+import android.support.v4.view.ViewCompat;
+import android.support.v4.view.ViewPropertyAnimatorCompat;
+import android.support.v4.view.ViewPropertyAnimatorListener;
+import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.SimpleItemAnimator;
+import android.view.View;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This basically follows the approach taken by Wasabeef:
+ *   <a href="https://github.com/wasabeef/recyclerview-animators">https://github.com/wasabeef/recyclerview-animators</a>
+ * based off of Android's DefaultItemAnimator from October 2016:
+ *   <a href="https://github.com/android/platform_frameworks_support/blob/432f3317f8a9b8cf98277938ea5df4021e983055/v7/recyclerview/src/android/support/v7/widget/DefaultItemAnimator.java">
+ *     https://github.com/android/platform_frameworks_support/blob/432f3317f8a9b8cf98277938ea5df4021e983055/v7/recyclerview/src/android/support/v7/widget/DefaultItemAnimator.java
+ *   </a>
+ * <p>
+ * Usage Notes:
+ * </p>
+ * <ul>
+ *   <li>You <strong>must</strong> add a Default*VpaListener to your animate*Impl animation - the
+ *       listener takes care of animation bookkeeping.</li>
+ *   <li>You should call {@link #resetAnimation(RecyclerView.ViewHolder)} at some point in
+ *       preAnimate*Impl if you choose to proceed with the animation. Some animations will want to
+ *       know some or all of the current animation values for initializing their own animation
+ *       values before resetting the current animation, so this class does not provide the reset
+ *       service itself.</li>
+ *   <li>{@link #resetViewProperties(View)} is used to reset a view any time an animation ends or
+ *       gets canceled - you should redefine resetViewProperties if the version here doesn't reset
+ *       all of the properties you're animating.</li>
+ * </ul>
+ */
+public class DefaultItemAnimatorBase extends SimpleItemAnimator {
+    private List<RecyclerView.ViewHolder> pendingRemovals = new ArrayList<>();
+    private List<RecyclerView.ViewHolder> pendingAdditions = new ArrayList<>();
+    private List<MoveInfo> pendingMoves = new ArrayList<>();
+    private List<ChangeInfo> pendingChanges = new ArrayList<>();
+
+    private List<List<RecyclerView.ViewHolder>> additionsList = new ArrayList<>();
+    private List<List<MoveInfo>> movesList = new ArrayList<>();
+    private List<List<ChangeInfo>> changesList = new ArrayList<>();
+
+    private List<RecyclerView.ViewHolder> addAnimations = new ArrayList<>();
+    private List<RecyclerView.ViewHolder> moveAnimations = new ArrayList<>();
+    private List<RecyclerView.ViewHolder> removeAnimations = new ArrayList<>();
+    private List<RecyclerView.ViewHolder> changeAnimations = new ArrayList<>();
+
+    protected static class MoveInfo {
+        public RecyclerView.ViewHolder holder;
+        public int fromX, fromY, toX, toY;
+
+        public MoveInfo(RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
+            this.holder = holder;
+            this.fromX = fromX;
+            this.fromY = fromY;
+            this.toX = toX;
+            this.toY = toY;
+        }
+    }
+
+    protected static class ChangeInfo {
+        public RecyclerView.ViewHolder oldHolder, newHolder;
+        public int fromX, fromY, toX, toY;
+
+        public ChangeInfo(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder) {
+            this.oldHolder = oldHolder;
+            this.newHolder = newHolder;
+        }
+
+        public ChangeInfo(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder,
+                           int fromX, int fromY, int toX, int toY) {
+            this(oldHolder, newHolder);
+            this.fromX = fromX;
+            this.fromY = fromY;
+            this.toX = toX;
+            this.toY = toY;
+        }
+
+        @Override
+        public String toString() {
+            return "ChangeInfo{" +
+                    "oldHolder=" + oldHolder +
+                    ", newHolder=" + newHolder +
+                    ", fromX=" + fromX +
+                    ", fromY=" + fromY +
+                    ", toX=" + toX +
+                    ", toY=" + toY +
+                    '}';
+        }
+    }
+
+    @Override
+    public void runPendingAnimations() {
+        final boolean removalsPending = !pendingRemovals.isEmpty();
+        final boolean movesPending = !pendingMoves.isEmpty();
+        final boolean changesPending = !pendingChanges.isEmpty();
+        final boolean additionsPending = !pendingAdditions.isEmpty();
+        if (!removalsPending && !movesPending && !additionsPending && !changesPending) {
+            return;
+        }
+        // First, remove stuff.
+        for (final RecyclerView.ViewHolder holder : pendingRemovals) {
+            animateRemoveImpl(holder);
+        }
+        pendingRemovals.clear();
+        // Next, move stuff.
+        if (movesPending) {
+            final List<MoveInfo> moves = new ArrayList<>();
+            moves.addAll(pendingMoves);
+            movesList.add(moves);
+            pendingMoves.clear();
+            final Runnable mover = new Runnable() {
+                @Override
+                public void run() {
+                    for (final MoveInfo moveInfo : moves) {
+                        animateMoveImpl(moveInfo.holder, moveInfo.fromX, moveInfo.fromY,
+                                moveInfo.toX, moveInfo.toY);
+                    }
+                    moves.clear();
+                    movesList.remove(moves);
+                }
+            };
+            if (removalsPending) {
+                final View view = moves.get(0).holder.itemView;
+                ViewCompat.postOnAnimationDelayed(view, mover, getRemoveDuration());
+            } else {
+                mover.run();
+            }
+        }
+        // Next, change stuff, to run in parallel with move animations.
+        if (changesPending) {
+            final List<ChangeInfo> changes = new ArrayList<>();
+            changes.addAll(pendingChanges);
+            changesList.add(changes);
+            pendingChanges.clear();
+            final Runnable changer = new Runnable() {
+                @Override
+                public void run() {
+                    for (final ChangeInfo change : changes) {
+                        animateChangeImpl(change);
+                    }
+                    changes.clear();
+                    changesList.remove(changes);
+                }
+            };
+            if (removalsPending) {
+                RecyclerView.ViewHolder holder = changes.get(0).oldHolder;
+                ViewCompat.postOnAnimationDelayed(holder.itemView, changer, getRemoveDuration());
+            } else {
+                changer.run();
+            }
+        }
+        // Next, add stuff.
+        if (additionsPending) {
+            final List<RecyclerView.ViewHolder> additions = new ArrayList<>();
+            additions.addAll(pendingAdditions);
+            additionsList.add(additions);
+            pendingAdditions.clear();
+            final Runnable adder = new Runnable() {
+                public void run() {
+                    for (final RecyclerView.ViewHolder holder : additions) {
+                        animateAddImpl(holder);
+                    }
+                    additions.clear();
+                    additionsList.remove(additions);
+                }
+            };
+            if (removalsPending || movesPending || changesPending) {
+                final long removeDuration = removalsPending ? getRemoveDuration() : 0;
+                final long moveDuration = movesPending ? getMoveDuration() : 0;
+                final long changeDuration = changesPending ? getChangeDuration() : 0;
+                final long totalDelay = removeDuration + Math.max(moveDuration, changeDuration);
+                final View view = additions.get(0).itemView;
+                ViewCompat.postOnAnimationDelayed(view, adder, totalDelay);
+            } else {
+                adder.run();
+            }
+        }
+    }
+
+    @Override
+    public boolean animateRemove(final RecyclerView.ViewHolder holder) {
+        if (!preAnimateRemoveImpl(holder)) {
+            dispatchRemoveFinished(holder);
+            return false;
+        }
+        pendingRemovals.add(holder);
+        return true;
+    }
+
+    protected boolean preAnimateRemoveImpl(final RecyclerView.ViewHolder holder) {
+        resetAnimation(holder);
+        return true;
+    }
+
+    protected void animateRemoveImpl(final RecyclerView.ViewHolder holder) {
+        ViewCompat.animate(holder.itemView)
+                .setDuration(getRemoveDuration())
+                .alpha(0)
+                .setListener(new DefaultRemoveVpaListener(holder))
+                .start();
+    }
+
+    @Override
+    public boolean animateAdd(final RecyclerView.ViewHolder holder) {
+        if (!preAnimateAddImpl(holder)) {
+            dispatchAddFinished(holder);
+            return false;
+        }
+        pendingAdditions.add(holder);
+        return true;
+    }
+
+    protected boolean preAnimateAddImpl(RecyclerView.ViewHolder holder) {
+        resetAnimation(holder);
+        holder.itemView.setAlpha(0);
+        return true;
+    }
+
+    protected void animateAddImpl(final RecyclerView.ViewHolder holder) {
+        ViewCompat.animate(holder.itemView)
+                .setDuration(getAddDuration())
+                .alpha(1)
+                .setListener(new DefaultAddVpaListener(holder))
+                .start();
+    }
+
+    @Override
+    public boolean animateMove(final RecyclerView.ViewHolder holder,
+                               int fromX, int fromY, int toX, int toY) {
+        final View view = holder.itemView;
+        fromX += ViewCompat.getTranslationX(holder.itemView);
+        fromY += ViewCompat.getTranslationY(holder.itemView);
+        final int deltaX = toX - fromX;
+        final int deltaY = toY - fromY;
+        if (deltaX == 0 && deltaY == 0) {
+            dispatchMoveFinished(holder);
+            return false;
+        }
+        resetAnimation(holder);
+        if (deltaX != 0) {
+            ViewCompat.setTranslationX(view, -deltaX);
+        }
+        if (deltaY != 0) {
+            ViewCompat.setTranslationY(view, -deltaY);
+        }
+        pendingMoves.add(new MoveInfo(holder, fromX, fromY, toX, toY));
+        return true;
+    }
+
+    protected void animateMoveImpl(final RecyclerView.ViewHolder holder,
+                                   int fromX, int fromY, int toX, int toY) {
+        final View view = holder.itemView;
+        final int deltaX = toX - fromX;
+        final int deltaY = toY - fromY;
+        if (deltaX != 0) {
+            ViewCompat.animate(view).translationX(0);
+        }
+        if (deltaY != 0) {
+            ViewCompat.animate(view).translationY(0);
+        }
+        // TODO: make EndActions end listeners instead, since end actions aren't called when
+        // vpas are canceled (and can't end them. why?)
+        // need listener functionality in VPACompat for this. Ick.
+        final ViewPropertyAnimatorCompat animation = ViewCompat.animate(view);
+        moveAnimations.add(holder);
+        animation.setDuration(getMoveDuration()).setListener(new VpaListenerAdapter() {
+            @Override
+            public void onAnimationStart(View view) {
+                dispatchMoveStarting(holder);
+            }
+            @Override
+            public void onAnimationCancel(View view) {
+                resetViewProperties(view);
+            }
+            @Override
+            public void onAnimationEnd(View view) {
+                animation.setListener(null);
+                dispatchMoveFinished(holder);
+                moveAnimations.remove(holder);
+                dispatchFinishedWhenDone();
+            }
+        }).start();
+    }
+
+    @Override
+    public boolean animateChange(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder,
+                                 int fromX, int fromY, int toX, int toY) {
+        if (oldHolder == newHolder) {
+            // Don't know how to run change animations when the same view holder is re-used.
+            // Run a move animation to handle position changes (if there are any).
+            if (fromX != toX || fromY != toY) {
+                // *Don't* call dispatchChangeFinished here, it leads to unbalanced isRecyclable calls.
+                return animateMove(oldHolder, fromX, fromY, toX, toY);
+            }
+            dispatchChangeFinished(oldHolder, true);
+            return false;
+        }
+        final float prevTranslationX = ViewCompat.getTranslationX(oldHolder.itemView);
+        final float prevTranslationY = ViewCompat.getTranslationY(oldHolder.itemView);
+        final float prevAlpha = ViewCompat.getAlpha(oldHolder.itemView);
+        resetAnimation(oldHolder);
+        final int deltaX = (int) (toX - fromX - prevTranslationX);
+        final int deltaY = (int) (toY - fromY - prevTranslationY);
+        // Recover previous translation state after ending animation.
+        ViewCompat.setTranslationX(oldHolder.itemView, prevTranslationX);
+        ViewCompat.setTranslationY(oldHolder.itemView, prevTranslationY);
+        ViewCompat.setAlpha(oldHolder.itemView, prevAlpha);
+        if (newHolder != null) {
+            // Carry over translation values.
+            resetAnimation(newHolder);
+            ViewCompat.setTranslationX(newHolder.itemView, -deltaX);
+            ViewCompat.setTranslationY(newHolder.itemView, -deltaY);
+            ViewCompat.setAlpha(newHolder.itemView, 0);
+        }
+        pendingChanges.add(new ChangeInfo(oldHolder, newHolder, fromX, fromY, toX, toY));
+        return true;
+    }
+
+    protected void animateChangeImpl(final ChangeInfo changeInfo) {
+        final RecyclerView.ViewHolder holder = changeInfo.oldHolder;
+        final View view = holder == null ? null : holder.itemView;
+        final RecyclerView.ViewHolder newHolder = changeInfo.newHolder;
+        final View newView = newHolder != null ? newHolder.itemView : null;
+        if (view != null) {
+            final ViewPropertyAnimatorCompat oldViewAnim = ViewCompat.animate(view).setDuration(
+                    getChangeDuration());
+            changeAnimations.add(changeInfo.oldHolder);
+            oldViewAnim.translationX(changeInfo.toX - changeInfo.fromX);
+            oldViewAnim.translationY(changeInfo.toY - changeInfo.fromY);
+            oldViewAnim.alpha(0).setListener(new VpaListenerAdapter() {
+                @Override
+                public void onAnimationStart(View view) {
+                    dispatchChangeStarting(changeInfo.oldHolder, true);
+                }
+
+                @Override
+                public void onAnimationEnd(View view) {
+                    oldViewAnim.setListener(null);
+                    resetViewProperties(view);
+                    dispatchChangeFinished(changeInfo.oldHolder, true);
+                    changeAnimations.remove(changeInfo.oldHolder);
+                    dispatchFinishedWhenDone();
+                }
+            }).start();
+        }
+        if (newView != null) {
+            final ViewPropertyAnimatorCompat newViewAnimation = ViewCompat.animate(newView);
+            changeAnimations.add(changeInfo.newHolder);
+            newViewAnimation.translationX(0).translationY(0).setDuration(getChangeDuration()).
+                    alpha(1).setListener(new VpaListenerAdapter() {
+                @Override
+                public void onAnimationStart(View view) {
+                    dispatchChangeStarting(changeInfo.newHolder, false);
+                }
+                @Override
+                public void onAnimationEnd(View view) {
+                    newViewAnimation.setListener(null);
+                    resetViewProperties(view);
+                    dispatchChangeFinished(changeInfo.newHolder, false);
+                    changeAnimations.remove(changeInfo.newHolder);
+                    dispatchFinishedWhenDone();
+                }
+            }).start();
+}
+    }
+
+    private void endChangeAnimation(List<ChangeInfo> infoList, RecyclerView.ViewHolder item) {
+        for (int i = infoList.size() - 1; i >= 0; i--) {
+            final ChangeInfo changeInfo = infoList.get(i);
+            if (endChangeAnimationIfNecessary(changeInfo, item)) {
+                if (changeInfo.oldHolder == null && changeInfo.newHolder == null) {
+                    infoList.remove(changeInfo);
+                }
+            }
+        }
+    }
+
+    private void endChangeAnimationIfNecessary(ChangeInfo changeInfo) {
+        if (changeInfo.oldHolder != null) {
+            endChangeAnimationIfNecessary(changeInfo, changeInfo.oldHolder);
+        }
+        if (changeInfo.newHolder != null) {
+            endChangeAnimationIfNecessary(changeInfo, changeInfo.newHolder);
+        }
+    }
+
+    private boolean endChangeAnimationIfNecessary(ChangeInfo changeInfo, RecyclerView.ViewHolder item) {
+        boolean oldItem = false;
+        if (changeInfo.newHolder == item) {
+            changeInfo.newHolder = null;
+        } else if (changeInfo.oldHolder == item) {
+            changeInfo.oldHolder = null;
+            oldItem = true;
+        } else {
+            return false;
+        }
+        resetViewProperties(item.itemView);
+        dispatchChangeFinished(item, oldItem);
+        return true;
+    }
+
+    /**
+     * Called to reset all properties possibly animated by any and all defined animations.
+     */
+    protected void resetViewProperties(View view) {
+        view.setTranslationX(0);
+        view.setTranslationY(0);
+        view.setAlpha(1);
+    }
+
+    @Override
+    public void endAnimation(RecyclerView.ViewHolder item) {
+
+        final View view = item.itemView;
+        // This calls dispatch*Finished, resets view properties, and removes item from current
+        // animations list if the view is currently being animated.
+        ViewCompat.animate(view).cancel();
+        // TODO if some other animations are chained to end, how do we cancel them as well?
+        for (int i = pendingMoves.size() - 1; i >= 0; i--) {
+            final MoveInfo moveInfo = pendingMoves.get(i);
+            if (moveInfo.holder == item) {
+                resetViewProperties(view);
+                dispatchMoveFinished(item);
+                pendingMoves.remove(i);
+            }
+        }
+        endChangeAnimation(pendingChanges, item);
+        if (pendingRemovals.remove(item)) {
+            resetViewProperties(view);
+            dispatchRemoveFinished(item);
+        }
+        if (pendingAdditions.remove(item)) {
+            resetViewProperties(view);
+            dispatchAddFinished(item);
+        }
+
+        for (int i = changesList.size() - 1; i >= 0; i--) {
+            final List<ChangeInfo> changes = changesList.get(i);
+            endChangeAnimation(changes, item);
+            if (changes.isEmpty()) {
+                changesList.remove(i);
+            }
+        }
+        for (int i = movesList.size() - 1; i >= 0; i--) {
+            final List<MoveInfo> moves = movesList.get(i);
+            for (int j = moves.size() - 1; j >= 0; j--) {
+                final MoveInfo moveInfo = moves.get(j);
+                if (moveInfo.holder == item) {
+                    resetViewProperties(view);
+                    dispatchMoveFinished(item);
+                    moves.remove(j);
+                    if (moves.isEmpty()) {
+                        movesList.remove(i);
+                    }
+                    break;
+                }
+            }
+        }
+        for (int i = additionsList.size() - 1; i >= 0; i--) {
+            final List<RecyclerView.ViewHolder> additions = additionsList.get(i);
+            if (additions.remove(item)) {
+                resetViewProperties(view);
+                dispatchAddFinished(item);
+                if (additions.isEmpty()) {
+                    additionsList.remove(i);
+                }
+            }
+        }
+        dispatchFinishedWhenDone();
+    }
+
+    protected void resetAnimation(RecyclerView.ViewHolder holder) {
+        AnimatorCompatHelper.clearInterpolator(holder.itemView);
+        endAnimation(holder);
+    }
+
+    @Override
+    public boolean isRunning() {
+        return (!pendingAdditions.isEmpty() ||
+                !pendingChanges.isEmpty() ||
+                !pendingMoves.isEmpty() ||
+                !pendingRemovals.isEmpty() ||
+                !moveAnimations.isEmpty() ||
+                !removeAnimations.isEmpty() ||
+                !addAnimations.isEmpty() ||
+                !changeAnimations.isEmpty() ||
+                !movesList.isEmpty() ||
+                !additionsList.isEmpty() ||
+                !changesList.isEmpty());
+    }
+
+    /**
+     * Check the state of currently pending and running animations. If there are none
+     * pending/running, call {@link #dispatchAnimationsFinished()} to notify any
+     * listeners.
+     */
+    protected void dispatchFinishedWhenDone() {
+        if (!isRunning()) {
+            dispatchAnimationsFinished();
+        }
+    }
+
+    @Override
+    public void endAnimations() {
+        int count = pendingMoves.size();
+        for (int i = count - 1; i >= 0; i--) {
+            final MoveInfo item = pendingMoves.get(i);
+            resetViewProperties(item.holder.itemView);
+            dispatchMoveFinished(item.holder);
+            pendingMoves.remove(i);
+        }
+        count = pendingRemovals.size();
+        for (int i = count - 1; i >= 0; i--) {
+            final RecyclerView.ViewHolder item = pendingRemovals.get(i);
+            resetViewProperties(item.itemView);
+            dispatchRemoveFinished(item);
+            pendingRemovals.remove(i);
+        }
+        count = pendingAdditions.size();
+        for (int i = count - 1; i >= 0; i--) {
+            final RecyclerView.ViewHolder item = pendingAdditions.get(i);
+            resetViewProperties(item.itemView);
+            dispatchAddFinished(item);
+            pendingAdditions.remove(i);
+        }
+        count = pendingChanges.size();
+        for (int i = count - 1; i >= 0; i--) {
+            endChangeAnimationIfNecessary(pendingChanges.get(i));
+        }
+        pendingChanges.clear();
+        if (!isRunning()) {
+            return;
+        }
+
+        int listCount = movesList.size();
+        for (int i = listCount - 1; i >= 0; i--) {
+            final List<MoveInfo> moves = movesList.get(i);
+            count = moves.size();
+            for (int j = count - 1; j >= 0; j--) {
+                final MoveInfo moveInfo = moves.get(j);
+                final RecyclerView.ViewHolder item = moveInfo.holder;
+                resetViewProperties(item.itemView);
+                dispatchMoveFinished(item);
+                moves.remove(j);
+                if (moves.isEmpty()) {
+                    movesList.remove(moves);
+                }
+            }
+        }
+        listCount = additionsList.size();
+        for (int i = listCount - 1; i >= 0; i--) {
+            final List<RecyclerView.ViewHolder> additions = additionsList.get(i);
+            count = additions.size();
+            for (int j = count - 1; j >= 0; j--) {
+                final RecyclerView.ViewHolder item = additions.get(j);
+                resetViewProperties(item.itemView);
+                dispatchAddFinished(item);
+                additions.remove(j);
+                if (additions.isEmpty()) {
+                    additionsList.remove(additions);
+                }
+            }
+        }
+        listCount = changesList.size();
+        for (int i = listCount - 1; i >= 0; i--) {
+            final List<ChangeInfo> changes = changesList.get(i);
+            count = changes.size();
+            for (int j = count - 1; j >= 0; j--) {
+                endChangeAnimationIfNecessary(changes.get(j));
+                if (changes.isEmpty()) {
+                    changesList.remove(changes);
+                }
+            }
+        }
+
+        cancelAll(removeAnimations);
+        cancelAll(moveAnimations);
+        cancelAll(addAnimations);
+        cancelAll(changeAnimations);
+
+        dispatchAnimationsFinished();
+    }
+
+    public void cancelAll(List<RecyclerView.ViewHolder> viewHolders) {
+        for (int i = viewHolders.size() - 1; i >= 0; i--) {
+            ViewCompat.animate(viewHolders.get(i).itemView).cancel();
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     * <p>
+     * If the payload list is not empty, DefaultItemAnimator returns <code>true</code>.
+     * When this is the case:
+     * <ul>
+     * <li>If you override
+     * {@link #animateChange(RecyclerView.ViewHolder, RecyclerView.ViewHolder, int, int, int, int)},
+     * both ViewHolder arguments will be the same instance.
+     * </li>
+     * <li>
+     * If you are not overriding
+     * {@link #animateChange(RecyclerView.ViewHolder, RecyclerView.ViewHolder, int, int, int, int)},
+     * then DefaultItemAnimator will call
+     * {@link #animateMove(RecyclerView.ViewHolder, int, int, int, int)} and run a move animation
+     * instead.
+     * </li>
+     * </ul>
+     */
+    @Override
+    public boolean canReuseUpdatedViewHolder(@NonNull RecyclerView.ViewHolder viewHolder,
+            @NonNull List<Object> payloads) {
+        return !payloads.isEmpty() || super.canReuseUpdatedViewHolder(viewHolder, payloads);
+    }
+
+    private class VpaListenerAdapter implements ViewPropertyAnimatorListener {
+        @Override
+        public void onAnimationStart(View view) {}
+
+        // Note that onAnimationEnd is called (in addition to OnAnimationCancel) whenever an
+        // animation is canceled.
+        @Override
+        public void onAnimationEnd(View view) {
+            resetViewProperties(view);
+            view.animate().setListener(null);
+        }
+
+        @Override
+        public void onAnimationCancel(View view) {}
+    }
+
+    protected class DefaultRemoveVpaListener extends VpaListenerAdapter {
+        private final RecyclerView.ViewHolder viewHolder;
+
+        public DefaultRemoveVpaListener(final RecyclerView.ViewHolder holder) {
+            viewHolder = holder;
+        }
+
+        @Override
+        public void onAnimationStart(View view) {
+            removeAnimations.add(viewHolder);
+            dispatchRemoveStarting(viewHolder);
+        }
+
+        @Override
+        public void onAnimationEnd(View view) {
+            removeAnimations.remove(viewHolder);
+            dispatchRemoveFinished(viewHolder);
+            dispatchFinishedWhenDone();
+            super.onAnimationEnd(view);
+        }
+    }
+
+    protected class DefaultAddVpaListener extends VpaListenerAdapter {
+        private final RecyclerView.ViewHolder viewHolder;
+
+        public DefaultAddVpaListener(final RecyclerView.ViewHolder holder) {
+            viewHolder = holder;
+        }
+
+        @Override
+        public void onAnimationStart(View view) {
+            addAnimations.add(viewHolder);
+            dispatchAddStarting(viewHolder);
+        }
+
+        @Override
+        public void onAnimationEnd(View view) {
+            addAnimations.remove(viewHolder);
+            dispatchAddFinished(viewHolder);
+            dispatchFinishedWhenDone();
+            super.onAnimationEnd(view);
+        }
+    }
+}

--- a/mobile/android/base/moz.build
+++ b/mobile/android/base/moz.build
@@ -732,16 +732,17 @@ gbjar.sources += ['java/org/mozilla/geck
     'widget/AnimatedHeightLayout.java',
     'widget/BasicColorPicker.java',
     'widget/CheckableLinearLayout.java',
     'widget/ClickableWhenDisabledEditText.java',
     'widget/ContentSecurityDoorHanger.java',
     'widget/CropImageView.java',
     'widget/DateTimePicker.java',
     'widget/DefaultDoorHanger.java',
+    'widget/DefaultItemAnimatorBase.java',
     'widget/DoorHanger.java',
     'widget/DoorhangerConfig.java',
     'widget/EllipsisTextView.java',
     'widget/ExternalIntentDuringPrivateBrowsingPromptFragment.java',
     'widget/FadedMultiColorTextView.java',
     'widget/FadedSingleColorTextView.java',
     'widget/FadedTextView.java',
     'widget/FaviconView.java',