From 04a00867d20b041b5b4cb55b76edf5468bd442d3 Mon Sep 17 00:00:00 2001
From: Wes Kocher <wkocher@mozilla.com>
Date: Thu, 26 Feb 2015 17:56:14 -0800
Subject: [PATCH] Backed out 2 changesets (bug 995394) for m-dt orange on a
 CLOSED TREE

Backed out changeset a250f116b563 (bug 995394)
Backed out changeset da37f3c9b4ce (bug 995394)
---
 dom/browser-element/BrowserElementChild.js    |   8 -
 dom/browser-element/BrowserElementPanning.js  | 657 +++++++++++++++++
 .../BrowserElementPanningAPZDisabled.js       | 675 ------------------
 dom/ipc/jar.mn                                |   1 -
 dom/ipc/preload.js                            |   7 -
 5 files changed, 657 insertions(+), 691 deletions(-)
 delete mode 100644 dom/browser-element/BrowserElementPanningAPZDisabled.js

diff --git a/dom/browser-element/BrowserElementChild.js b/dom/browser-element/BrowserElementChild.js
index d93b2002d204..81747115e43f 100644
--- a/dom/browser-element/BrowserElementChild.js
+++ b/dom/browser-element/BrowserElementChild.js
@@ -42,19 +42,11 @@ if (!('BrowserElementIsPreloaded' in this)) {
     }
   }
 
-  if (docShell.asyncPanZoomEnabled === false) {
-    Services.scriptloader.loadSubScript("chrome://global/content/BrowserElementPanningAPZDisabled.js");
-    ContentPanningAPZDisabled.init();
-  }
-
   Services.scriptloader.loadSubScript("chrome://global/content/BrowserElementPanning.js");
   ContentPanning.init();
 
   Services.scriptloader.loadSubScript("chrome://global/content/BrowserElementChildPreload.js");
 } else {
-  if (docShell.asyncPanZoomEnabled === false) {
-    ContentPanningAPZDisabled.init();
-  }
   ContentPanning.init();
 }
 
diff --git a/dom/browser-element/BrowserElementPanning.js b/dom/browser-element/BrowserElementPanning.js
index 3800c505575a..828a430b1098 100644
--- a/dom/browser-element/BrowserElementPanning.js
+++ b/dom/browser-element/BrowserElementPanning.js
@@ -12,6 +12,8 @@ let { classes: Cc, interfaces: Ci, results: Cr, utils: Cu }  = Components;
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/Geometry.jsm");
 
+var global = this;
+
 const kObservedEvents = [
   "BEC:ShownModalPrompt",
   "Activity:Success",
@@ -19,7 +21,21 @@ const kObservedEvents = [
 ];
 
 const ContentPanning = {
+  // Are we listening to touch or mouse events?
+  watchedEventsType: '',
+
+  // Are mouse events being delivered to this content along with touch
+  // events, in violation of spec?
+  hybridEvents: false,
+
   init: function cp_init() {
+    // If APZ is enabled, we do active element handling in C++
+    // (see widget/xpwidgets/ActiveElementManager.h), and panning
+    // itself in APZ, so we don't need to handle any touch events here.
+    if (docShell.asyncPanZoomEnabled === false) {
+      this._setupListenersForPanning();
+    }
+
     addEventListener("unload",
 		     this._unloadHandler.bind(this),
 		     /* useCapture = */ false,
@@ -33,16 +49,441 @@ const ContentPanning = {
     });
   },
 
+  _setupListenersForPanning: function cp_setupListenersForPanning() {
+    let events;
+
+    if (content.TouchEvent) {
+      events = ['touchstart', 'touchend', 'touchmove'];
+      this.watchedEventsType = 'touch';
+#ifdef MOZ_WIDGET_GONK
+      // The gonk widget backend does not deliver mouse events per
+      // spec.  Third-party content isn't exposed to this behavior,
+      // but that behavior creates some extra work for us here.
+      let appInfo = Cc["@mozilla.org/xre/app-info;1"];
+      let isParentProcess =
+        !appInfo || appInfo.getService(Ci.nsIXULRuntime)
+                           .processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+      this.hybridEvents = isParentProcess;
+#endif
+    } else {
+      // Touch events aren't supported, so fall back on mouse.
+      events = ['mousedown', 'mouseup', 'mousemove'];
+      this.watchedEventsType = 'mouse';
+    }
+
+    let els = Cc["@mozilla.org/eventlistenerservice;1"]
+                .getService(Ci.nsIEventListenerService);
+
+    events.forEach(function(type) {
+      // Using the system group for mouse/touch events to avoid
+      // missing events if .stopPropagation() has been called.
+      els.addSystemEventListener(global, type,
+                                 this.handleEvent.bind(this),
+                                 /* useCapture = */ false);
+    }.bind(this));
+  },
+
+  handleEvent: function cp_handleEvent(evt) {
+    // Ignore events targeting an oop <iframe mozbrowser> since those will be
+    // handle by the BrowserElementPanning.js instance in the child process.
+    if (evt.target instanceof Ci.nsIMozBrowserFrame) {
+      return;
+    }
+
+    // For in-process <iframe mozbrowser> the events are not targetting
+    // directly the container iframe element, but some node of the document.
+    // So, the BrowserElementPanning instance of the system app will receive
+    // the sequence of touch events, as well as the BrowserElementPanning
+    // instance in the targetted app.
+    // As a result, multiple mozbrowser iframes will try to interpret the
+    // sequence of touch events, which may results into multiple clicks.
+    let targetWindow = evt.target.ownerDocument.defaultView;
+    let frameElement = targetWindow.frameElement;
+    while (frameElement) {
+      targetWindow = frameElement.ownerDocument.defaultView;
+      frameElement = targetWindow.frameElement;
+    }
+
+    if (content !== targetWindow) {
+      return;
+    }
+
+    if (evt.defaultPrevented || evt.multipleActionsPrevented) {
+      // clean up panning state even if touchend/mouseup has been preventDefault.
+      if(evt.type === 'touchend' || evt.type === 'mouseup') {
+        if (this.dragging &&
+            (this.watchedEventsType === 'mouse' ||
+             this.findPrimaryPointer(evt.changedTouches))) {
+          this._finishPanning();
+        }
+      }
+      return;
+    }
+
+    switch (evt.type) {
+      case 'mousedown':
+      case 'touchstart':
+        this.onTouchStart(evt);
+        break;
+      case 'mousemove':
+      case 'touchmove':
+        this.onTouchMove(evt);
+        break;
+      case 'mouseup':
+      case 'touchend':
+        this.onTouchEnd(evt);
+        break;
+      case 'click':
+        evt.stopPropagation();
+        evt.preventDefault();
+
+        let target = evt.target;
+        let view = target.ownerDocument ? target.ownerDocument.defaultView
+                                        : target;
+        view.removeEventListener('click', this, true, true);
+        break;
+    }
+  },
+
   observe: function cp_observe(subject, topic, data) {
     this._resetHover();
   },
 
+  position: new Point(0 , 0),
+
+  findPrimaryPointer: function cp_findPrimaryPointer(touches) {
+    if (!('primaryPointerId' in this))
+      return null;
+
+    for (let i = 0; i < touches.length; i++) {
+      if (touches[i].identifier === this.primaryPointerId) {
+        return touches[i];
+      }
+    }
+    return null;
+  },
+
+  onTouchStart: function cp_onTouchStart(evt) {
+    let screenX, screenY;
+    if (this.watchedEventsType == 'touch') {
+      if ('primaryPointerId' in this || evt.touches.length >= 2) {
+        this._resetActive();
+        return;
+      }
+
+      let firstTouch = evt.changedTouches[0];
+      this.primaryPointerId = firstTouch.identifier;
+      this.pointerDownTarget = firstTouch.target;
+      screenX = firstTouch.screenX;
+      screenY = firstTouch.screenY;
+    } else {
+      this.pointerDownTarget = evt.target;
+      screenX = evt.screenX;
+      screenY = evt.screenY;
+    }
+    this.dragging = true;
+    this.panning = false;
+
+    let oldTarget = this.target;
+    [this.target, this.scrollCallback] = this.getPannable(this.pointerDownTarget);
+
+    // If we have a pointer down target, we may need to fill in for EventStateManager
+    // in setting the active state on the target element.  Set a timer to
+    // ensure the pointer-down target is active.  (If it's already
+    // active, the timer is a no-op.)
+    if (this.pointerDownTarget !== null) {
+      // If there's no possibility this is a drag/pan, activate now.
+      // Otherwise wait a little bit to see if the gesture isn't a
+      // tap.
+      if (this.target === null) {
+        this.notify(this._activationTimer);
+      } else {
+        this._activationTimer.initWithCallback(this,
+                                               this._activationDelayMs,
+                                               Ci.nsITimer.TYPE_ONE_SHOT);
+      }
+    }
+
+    // If there is a pan animation running (from a previous pan gesture) and
+    // the user touch back the screen, stop this animation immediatly and
+    // prevent the possible click action if the touch happens on the same
+    // target.
+    this.preventNextClick = false;
+    if (KineticPanning.active) {
+      KineticPanning.stop();
+
+      if (oldTarget && oldTarget == this.target)
+        this.preventNextClick = true;
+    }
+
+    this.position.set(screenX, screenY);
+    KineticPanning.reset();
+    KineticPanning.record(new Point(0, 0), evt.timeStamp);
+
+    // We prevent start events to avoid sending a focus event at the end of this
+    // touch series. See bug 889717.
+    if ((this.panning || this.preventNextClick)) {
+      evt.preventDefault();
+    }
+  },
+
+  onTouchEnd: function cp_onTouchEnd(evt) {
+    let touch = null;
+    if (!this.dragging ||
+        (this.watchedEventsType == 'touch' &&
+         !(touch = this.findPrimaryPointer(evt.changedTouches)))) {
+      return;
+    }
+
+    // !isPan() and evt.detail should always give the same answer here
+    // since they use the same heuristics, but use the native gecko
+    // computation when possible.
+    //
+    // NB: when we're using touch events, then !KineticPanning.isPan()
+    // => this.panning, so we'll never attempt to block the click
+    // event.  That's OK however, because we won't fire a synthetic
+    // click when we're using touch events and this touch series
+    // wasn't a "tap" gesture.
+    let click = (this.watchedEventsType == 'mouse') ?
+      evt.detail : !KineticPanning.isPan();
+    // Additionally, if we're seeing non-compliant hybrid events, a
+    // "real" click will be generated if we started and ended on the
+    // same element.
+    if (this.hybridEvents) {
+      let target =
+        content.document.elementFromPoint(touch.clientX, touch.clientY);
+      click |= (target === this.pointerDownTarget);
+    }
+
+    if (this.target && click && (this.panning || this.preventNextClick)) {
+      if (this.hybridEvents) {
+        let target = this.target;
+        let view = target.ownerDocument ? target.ownerDocument.defaultView
+                                        : target;
+        view.addEventListener('click', this, true, true);
+      } else {
+        // We prevent end events to avoid sending a focus event. See bug 889717.
+        evt.preventDefault();
+      }
+    } else if (this.target && click && !this.panning) {
+      this.notify(this._activationTimer);
+    }
+
+    this._finishPanning();
+
+    // Now that we're done, avoid entraining the thing we just panned.
+    this.pointerDownTarget = null;
+  },
+
+  onTouchMove: function cp_onTouchMove(evt) {
+    if (!this.dragging)
+      return;
+
+    let screenX, screenY;
+    if (this.watchedEventsType == 'touch') {
+      let primaryTouch = this.findPrimaryPointer(evt.changedTouches);
+      if (evt.touches.length > 1 || !primaryTouch)
+        return;
+      screenX = primaryTouch.screenX;
+      screenY = primaryTouch.screenY;
+    } else {
+      screenX = evt.screenX;
+      screenY = evt.screenY;
+    }
+
+    let current = this.position;
+    let delta = new Point(screenX - current.x, screenY - current.y);
+    current.set(screenX, screenY);
+
+    KineticPanning.record(delta, evt.timeStamp);
+
+    let isPan = KineticPanning.isPan();
+
+    // If we've detected a pan gesture, cancel the active state of the
+    // current target.
+    if (!this.panning && isPan) {
+      this._resetActive();
+    }
+
+    // There's no possibility of us panning anything.
+    if (!this.scrollCallback) {
+      return;
+    }
+
+    // Scroll manually.
+    this.scrollCallback(delta.scale(-1));
+
+    if (!this.panning && isPan) {
+      this.panning = true;
+      this._activationTimer.cancel();
+    }
+
+    if (this.panning) {
+      // Only do this when we're actually executing a pan gesture.
+      // Otherwise synthetic mouse events will be canceled.
+      evt.stopPropagation();
+      evt.preventDefault();
+    }
+  },
+
+  // nsITimerCallback
+  notify: function cp_notify(timer) {
+    this._setActive(this.pointerDownTarget);
+  },
+
+  onKineticBegin: function cp_onKineticBegin(evt) {
+  },
+
+  onKineticPan: function cp_onKineticPan(delta) {
+    return !this.scrollCallback(delta);
+  },
+
+  onKineticEnd: function cp_onKineticEnd() {
+    if (!this.dragging)
+      this.scrollCallback = null;
+  },
+
+  getPannable: function cp_getPannable(node) {
+    let pannableNode = this._findPannable(node);
+    if (pannableNode) {
+      return [pannableNode, this._generateCallback(pannableNode)];
+    }
+
+    return [null, null];
+  },
+
+  _findPannable: function cp_findPannable(node) {
+    if (!(node instanceof Ci.nsIDOMHTMLElement) || node.tagName == 'HTML') {
+      return null;
+    }
+
+    let nodeContent = node.ownerDocument.defaultView;
+    while (!(node instanceof Ci.nsIDOMHTMLBodyElement)) {
+      let style = nodeContent.getComputedStyle(node, null);
+
+      let overflow = [style.getPropertyValue('overflow'),
+                      style.getPropertyValue('overflow-x'),
+                      style.getPropertyValue('overflow-y')];
+
+      let rect = node.getBoundingClientRect();
+      let isAuto = (overflow.indexOf('auto') != -1 &&
+                   (rect.height < node.scrollHeight ||
+                    rect.width < node.scrollWidth));
+
+      let isScroll = (overflow.indexOf('scroll') != -1);
+
+      let isScrollableTextarea = (node.tagName == 'TEXTAREA' &&
+          (node.scrollHeight > node.clientHeight ||
+           node.scrollWidth > node.clientWidth ||
+           ('scrollLeftMax' in node && node.scrollLeftMax > 0) ||
+           ('scrollTopMax' in node && node.scrollTopMax > 0)));
+      if (isScroll || isAuto || isScrollableTextarea) {
+        return node;
+      }
+
+      node = node.parentNode;
+    }
+
+    if (nodeContent.scrollMaxX || nodeContent.scrollMaxY) {
+      return nodeContent;
+    }
+
+    if (nodeContent.frameElement) {
+      return this._findPannable(nodeContent.frameElement);
+    }
+
+    return null;
+  },
+
+  _generateCallback: function cp_generateCallback(root) {
+    let firstScroll = true;
+    let target;
+    let current;
+    let win, doc, htmlNode, bodyNode;
+
+    function doScroll(node, delta) {
+      if (node instanceof Ci.nsIDOMHTMLElement) {
+        return node.scrollByNoFlush(delta.x, delta.y);
+      } else if (node instanceof Ci.nsIDOMWindow) {
+        win = node;
+        doc = win.document;
+
+        // "overflow:hidden" on either the <html> or the <body> node should
+        // prevent the user from scrolling the root viewport.
+        if (doc instanceof Ci.nsIDOMHTMLDocument) {
+          htmlNode = doc.documentElement;
+          bodyNode = doc.body;
+          if (win.getComputedStyle(htmlNode, null).overflowX == "hidden" ||
+              win.getComputedStyle(bodyNode, null).overflowX == "hidden") {
+            delta.x = 0;
+          }
+          if (win.getComputedStyle(htmlNode, null).overflowY == "hidden" ||
+              win.getComputedStyle(bodyNode, null).overflowY == "hidden") {
+            delta.y = 0;
+          }
+        }
+        let oldX = node.scrollX;
+        let oldY = node.scrollY;
+        node.scrollBy(delta.x, delta.y);
+        return (node.scrollX != oldX || node.scrollY != oldY);
+      }
+      // If we get here, |node| isn't an HTML element and it's not a window,
+      // but findPannable apparently thought it was scrollable... What is it?
+      return false;
+    }
+
+    function targetParent(node) {
+      return node.parentNode || node.frameElement || null;
+    }
+
+    function scroll(delta) {
+      current = root;
+      firstScroll = true;
+      while (current) {
+        if (doScroll(current, delta)) {
+          firstScroll = false;
+          return true;
+        }
+
+        // TODO The current code looks for possible scrolling regions only if
+        // this is the first scroll action but this should be more dynamic.
+        if (!firstScroll) {
+          return false;
+        }
+
+        current = ContentPanning._findPannable(targetParent(current));
+      }
+
+      // There is nothing scrollable here.
+      return false;
+    }
+    return scroll;
+  },
+
   get _domUtils() {
     delete this._domUtils;
     return this._domUtils = Cc['@mozilla.org/inspector/dom-utils;1']
                               .getService(Ci.inIDOMUtils);
   },
 
+  get _activationTimer() {
+    delete this._activationTimer;
+    return this._activationTimer = Cc["@mozilla.org/timer;1"]
+                                     .createInstance(Ci.nsITimer);
+  },
+
+  get _activationDelayMs() {
+    let delay = Services.prefs.getIntPref('ui.touch_activation.delay_ms');
+    delete this._activationDelayMs;
+    return this._activationDelayMs = delay;
+  },
+
+  _resetActive: function cp_resetActive() {
+    let elt = this.pointerDownTarget || this.target;
+    let root = elt.ownerDocument || elt.document;
+    this._setActive(root.documentElement);
+  },
+
   _resetHover: function cp_resetHover() {
     const kStateHover = 0x00000004;
     try {
@@ -51,6 +492,11 @@ const ContentPanning = {
     } catch(e) {}
   },
 
+  _setActive: function cp_setActive(elt) {
+    const kStateActive = 0x00000001;
+    this._domUtils.setContentState(elt, kStateActive);
+  },
+
   _recvViewportChange: function(data) {
     let metrics = data.json;
     this._viewport = new Rect(metrics.x, metrics.y,
@@ -164,6 +610,17 @@ const ContentPanning = {
     return (showing > 0.9 && (ratioW > 0.9 || ratioH > 0.9)); 
   },
 
+  _finishPanning: function() {
+    this.dragging = false;
+    delete this.primaryPointerId;
+    this._activationTimer.cancel();
+
+    // If there is a scroll action, let's do a manual kinetic panning action.
+    if (this.panning) {
+      KineticPanning.start(this);
+    }
+  },
+
   _unloadHandler: function() {
     kObservedEvents.forEach((topic) => {
       Services.obs.removeObserver(this, topic);
@@ -171,6 +628,206 @@ const ContentPanning = {
   }
 };
 
+// Min/max velocity of kinetic panning. This is in pixels/millisecond.
+const kMinVelocity = 0.2;
+const kMaxVelocity = 6;
+
+// Constants that affect the "friction" of the scroll pane.
+const kExponentialC = 1000;
+const kPolynomialC = 100 / 1000000;
+
+// How often do we change the position of the scroll pane?
+// Too often and panning may jerk near the end.
+// Too little and panning will be choppy. In milliseconds.
+const kUpdateInterval = 16;
+
+// The numbers of momentums to use for calculating the velocity of the pan.
+// Those are taken from the end of the action
+const kSamples = 5;
+
+const KineticPanning = {
+  _position: new Point(0, 0),
+  _velocity: new Point(0, 0),
+  _acceleration: new Point(0, 0),
+
+  get active() {
+    return this.target !== null;
+  },
+
+  target: null,
+  start: function kp_start(target) {
+    this.target = target;
+
+    // Calculate the initial velocity of the movement based on user input
+    let momentums = this.momentums;
+    let flick = momentums[momentums.length - 1].time - momentums[0].time < 300;
+
+    let distance = new Point(0, 0);
+    momentums.forEach(function(momentum) {
+      distance.add(momentum.dx, momentum.dy);
+    });
+
+    function clampFromZero(x, min, max) {
+      if (x >= 0)
+        return Math.max(min, Math.min(max, x));
+      return Math.min(-min, Math.max(-max, x));
+    }
+
+    let elapsed = momentums[momentums.length - 1].time - momentums[0].time;
+    let velocityX = clampFromZero(distance.x / elapsed, 0, kMaxVelocity);
+    let velocityY = clampFromZero(distance.y / elapsed, 0, kMaxVelocity);
+
+    let velocity = this._velocity;
+    if (flick) {
+      // Very fast pan action that does not generate a click are very often pan
+      // action. If this is a small gesture then it will not move the view a lot
+      // and so it will be above the minimun threshold and not generate any
+      // kinetic panning. This does not look on a device since this is often
+      // a real gesture, so let's lower the velocity threshold for such moves.
+      velocity.set(velocityX, velocityY);
+    } else {
+      velocity.set(Math.abs(velocityX) < kMinVelocity ? 0 : velocityX,
+                   Math.abs(velocityY) < kMinVelocity ? 0 : velocityY);
+    }
+    this.momentums = [];
+
+    // Set acceleration vector to opposite signs of velocity
+    function sign(x) {
+      return x ? (x > 0 ? 1 : -1) : 0;
+    }
+
+    this._acceleration.set(velocity.clone().map(sign).scale(-kPolynomialC));
+
+    // Reset the position
+    this._position.set(0, 0);
+
+    this._startAnimation();
+
+    this.target.onKineticBegin();
+  },
+
+  stop: function kp_stop() {
+    this.reset();
+
+    if (!this.target)
+      return;
+
+    this.target.onKineticEnd();
+    this.target = null;
+  },
+
+  reset: function kp_reset() {
+    this.momentums = [];
+    this.distance.set(0, 0);
+  },
+
+  momentums: [],
+  record: function kp_record(delta, timestamp) {
+    this.momentums.push({ 'time': this._getTime(timestamp),
+                          'dx' : delta.x, 'dy' : delta.y });
+
+    // We only need to keep kSamples in this.momentums.
+    if (this.momentums.length > kSamples) {
+      this.momentums.shift();
+    }
+
+    this.distance.add(delta.x, delta.y);
+  },
+
+  _getTime: function kp_getTime(time) {
+    // Touch events generated by the platform or hand-made are defined in
+    // microseconds instead of milliseconds. Bug 77992 will fix this at the
+    // platform level.
+    if (time > Date.now()) {
+      return Math.floor(time / 1000);
+    } else {
+      return time;
+    }
+  },
+
+  get threshold() {
+    let dpi = content.QueryInterface(Ci.nsIInterfaceRequestor)
+                     .getInterface(Ci.nsIDOMWindowUtils)
+                     .displayDPI;
+
+    let threshold = Services.prefs.getIntPref('ui.dragThresholdX') / 240 * dpi;
+
+    delete this.threshold;
+    return this.threshold = threshold;
+  },
+
+  distance: new Point(0, 0),
+  isPan: function cp_isPan() {
+    return (Math.abs(this.distance.x) > this.threshold ||
+            Math.abs(this.distance.y) > this.threshold);
+  },
+
+  _startAnimation: function kp_startAnimation() {
+    let c = kExponentialC;
+    function getNextPosition(position, v, a, t) {
+      // Important traits for this function:
+      //   p(t=0) is 0
+      //   p'(t=0) is v0
+      //
+      // We use exponential to get a smoother stop, but by itself exponential
+      // is too smooth at the end. Adding a polynomial with the appropriate
+      // weight helps to balance
+      position.set(v.x * Math.exp(-t / c) * -c + a.x * t * t + v.x * c,
+                   v.y * Math.exp(-t / c) * -c + a.y * t * t + v.y * c);
+    }
+
+    let startTime = content.mozAnimationStartTime;
+    let elapsedTime = 0, targetedTime = 0, averageTime = 0;
+
+    let velocity = this._velocity;
+    let acceleration = this._acceleration;
+
+    let position = this._position;
+    let nextPosition = new Point(0, 0);
+    let delta = new Point(0, 0);
+
+    let callback = (function(timestamp) {
+      if (!this.target)
+        return;
+
+      // To make animation end fast enough but to keep smoothness, average the
+      // ideal time frame (smooth animation) with the actual time lapse
+      // (end fast enough).
+      // Animation will never take longer than 2 times the ideal length of time.
+      elapsedTime = timestamp - startTime;
+      targetedTime += kUpdateInterval;
+      averageTime = (targetedTime + elapsedTime) / 2;
+
+      // Calculate new position.
+      getNextPosition(nextPosition, velocity, acceleration, averageTime);
+      delta.set(Math.round(nextPosition.x - position.x),
+                Math.round(nextPosition.y - position.y));
+
+      // Test to see if movement is finished for each component.
+      if (delta.x * acceleration.x > 0)
+        delta.x = position.x = velocity.x = acceleration.x = 0;
+
+      if (delta.y * acceleration.y > 0)
+        delta.y = position.y = velocity.y = acceleration.y = 0;
+
+      if (velocity.equals(0, 0) || delta.equals(0, 0)) {
+        this.stop();
+        return;
+      }
+
+      position.add(delta);
+      if (this.target.onKineticPan(delta.scale(-1))) {
+        this.stop();
+        return;
+      }
+
+      content.mozRequestAnimationFrame(callback);
+    }).bind(this);
+
+    content.mozRequestAnimationFrame(callback);
+  }
+};
+
 const ElementTouchHelper = {
   anyElementFromPoint: function(aWindow, aX, aY) {
     let cwu = aWindow.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
diff --git a/dom/browser-element/BrowserElementPanningAPZDisabled.js b/dom/browser-element/BrowserElementPanningAPZDisabled.js
deleted file mode 100644
index 26d5af92fb15..000000000000
--- a/dom/browser-element/BrowserElementPanningAPZDisabled.js
+++ /dev/null
@@ -1,675 +0,0 @@
-/* -*- tab-width: 2; indent-tabs-mode: nil; js-indent-level: 2 -*- */
-/* vim: set ts=2 sw=2 sts=2 et: */
-
-/* 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";
-dump("############################### browserElementPanningAPZDisabled.js loaded\n");
-
-let { classes: Cc, interfaces: Ci, results: Cr, utils: Cu }  = Components;
-Cu.import("resource://gre/modules/Services.jsm");
-Cu.import("resource://gre/modules/Geometry.jsm");
-
-var global = this;
-
-const ContentPanningAPZDisabled = {
-  // Are we listening to touch or mouse events?
-  watchedEventsType: '',
-
-  // Are mouse events being delivered to this content along with touch
-  // events, in violation of spec?
-  hybridEvents: false,
-
-  init: function cp_init() {
-    this._setupListenersForPanning();
-  },
-
-  _setupListenersForPanning: function cp_setupListenersForPanning() {
-    let events;
-
-    if (content.TouchEvent) {
-      events = ['touchstart', 'touchend', 'touchmove'];
-      this.watchedEventsType = 'touch';
-#ifdef MOZ_WIDGET_GONK
-      // The gonk widget backend does not deliver mouse events per
-      // spec.  Third-party content isn't exposed to this behavior,
-      // but that behavior creates some extra work for us here.
-      let appInfo = Cc["@mozilla.org/xre/app-info;1"];
-      let isParentProcess =
-        !appInfo || appInfo.getService(Ci.nsIXULRuntime)
-                           .processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
-      this.hybridEvents = isParentProcess;
-#endif
-    } else {
-      // Touch events aren't supported, so fall back on mouse.
-      events = ['mousedown', 'mouseup', 'mousemove'];
-      this.watchedEventsType = 'mouse';
-    }
-
-    let els = Cc["@mozilla.org/eventlistenerservice;1"]
-                .getService(Ci.nsIEventListenerService);
-
-    events.forEach(function(type) {
-      // Using the system group for mouse/touch events to avoid
-      // missing events if .stopPropagation() has been called.
-      els.addSystemEventListener(global, type,
-                                 this.handleEvent.bind(this),
-                                 /* useCapture = */ false);
-    }.bind(this));
-  },
-
-  handleEvent: function cp_handleEvent(evt) {
-    // Ignore events targeting an oop <iframe mozbrowser> since those will be
-    // handle by the BrowserElementPanning.js instance in the child process.
-    if (evt.target instanceof Ci.nsIMozBrowserFrame) {
-      return;
-    }
-
-    // For in-process <iframe mozbrowser> the events are not targetting
-    // directly the container iframe element, but some node of the document.
-    // So, the BrowserElementPanning instance of the system app will receive
-    // the sequence of touch events, as well as the BrowserElementPanning
-    // instance in the targetted app.
-    // As a result, multiple mozbrowser iframes will try to interpret the
-    // sequence of touch events, which may results into multiple clicks.
-    let targetWindow = evt.target.ownerDocument.defaultView;
-    let frameElement = targetWindow.frameElement;
-    while (frameElement) {
-      targetWindow = frameElement.ownerDocument.defaultView;
-      frameElement = targetWindow.frameElement;
-    }
-
-    if (content !== targetWindow) {
-      return;
-    }
-
-    if (evt.defaultPrevented || evt.multipleActionsPrevented) {
-      // clean up panning state even if touchend/mouseup has been preventDefault.
-      if(evt.type === 'touchend' || evt.type === 'mouseup') {
-        if (this.dragging &&
-            (this.watchedEventsType === 'mouse' ||
-             this.findPrimaryPointer(evt.changedTouches))) {
-          this._finishPanning();
-        }
-      }
-      return;
-    }
-
-    switch (evt.type) {
-      case 'mousedown':
-      case 'touchstart':
-        this.onTouchStart(evt);
-        break;
-      case 'mousemove':
-      case 'touchmove':
-        this.onTouchMove(evt);
-        break;
-      case 'mouseup':
-      case 'touchend':
-        this.onTouchEnd(evt);
-        break;
-      case 'click':
-        evt.stopPropagation();
-        evt.preventDefault();
-
-        let target = evt.target;
-        let view = target.ownerDocument ? target.ownerDocument.defaultView
-                                        : target;
-        view.removeEventListener('click', this, true, true);
-        break;
-    }
-  },
-
-  position: new Point(0 , 0),
-
-  findPrimaryPointer: function cp_findPrimaryPointer(touches) {
-    if (!('primaryPointerId' in this))
-      return null;
-
-    for (let i = 0; i < touches.length; i++) {
-      if (touches[i].identifier === this.primaryPointerId) {
-        return touches[i];
-      }
-    }
-    return null;
-  },
-
-  onTouchStart: function cp_onTouchStart(evt) {
-    let screenX, screenY;
-    if (this.watchedEventsType == 'touch') {
-      if ('primaryPointerId' in this || evt.touches.length >= 2) {
-        this._resetActive();
-        return;
-      }
-
-      let firstTouch = evt.changedTouches[0];
-      this.primaryPointerId = firstTouch.identifier;
-      this.pointerDownTarget = firstTouch.target;
-      screenX = firstTouch.screenX;
-      screenY = firstTouch.screenY;
-    } else {
-      this.pointerDownTarget = evt.target;
-      screenX = evt.screenX;
-      screenY = evt.screenY;
-    }
-    this.dragging = true;
-    this.panning = false;
-
-    let oldTarget = this.target;
-    [this.target, this.scrollCallback] = this.getPannable(this.pointerDownTarget);
-
-    // If we have a pointer down target, we may need to fill in for EventStateManager
-    // in setting the active state on the target element.  Set a timer to
-    // ensure the pointer-down target is active.  (If it's already
-    // active, the timer is a no-op.)
-    if (this.pointerDownTarget !== null) {
-      // If there's no possibility this is a drag/pan, activate now.
-      // Otherwise wait a little bit to see if the gesture isn't a
-      // tap.
-      if (this.target === null) {
-        this.notify(this._activationTimer);
-      } else {
-        this._activationTimer.initWithCallback(this,
-                                               this._activationDelayMs,
-                                               Ci.nsITimer.TYPE_ONE_SHOT);
-      }
-    }
-
-    // If there is a pan animation running (from a previous pan gesture) and
-    // the user touch back the screen, stop this animation immediatly and
-    // prevent the possible click action if the touch happens on the same
-    // target.
-    this.preventNextClick = false;
-    if (KineticPanning.active) {
-      KineticPanning.stop();
-
-      if (oldTarget && oldTarget == this.target)
-        this.preventNextClick = true;
-    }
-
-    this.position.set(screenX, screenY);
-    KineticPanning.reset();
-    KineticPanning.record(new Point(0, 0), evt.timeStamp);
-
-    // We prevent start events to avoid sending a focus event at the end of this
-    // touch series. See bug 889717.
-    if ((this.panning || this.preventNextClick)) {
-      evt.preventDefault();
-    }
-  },
-
-  onTouchEnd: function cp_onTouchEnd(evt) {
-    let touch = null;
-    if (!this.dragging ||
-        (this.watchedEventsType == 'touch' &&
-         !(touch = this.findPrimaryPointer(evt.changedTouches)))) {
-      return;
-    }
-
-    // !isPan() and evt.detail should always give the same answer here
-    // since they use the same heuristics, but use the native gecko
-    // computation when possible.
-    //
-    // NB: when we're using touch events, then !KineticPanning.isPan()
-    // => this.panning, so we'll never attempt to block the click
-    // event.  That's OK however, because we won't fire a synthetic
-    // click when we're using touch events and this touch series
-    // wasn't a "tap" gesture.
-    let click = (this.watchedEventsType == 'mouse') ?
-      evt.detail : !KineticPanning.isPan();
-    // Additionally, if we're seeing non-compliant hybrid events, a
-    // "real" click will be generated if we started and ended on the
-    // same element.
-    if (this.hybridEvents) {
-      let target =
-        content.document.elementFromPoint(touch.clientX, touch.clientY);
-      click |= (target === this.pointerDownTarget);
-    }
-
-    if (this.target && click && (this.panning || this.preventNextClick)) {
-      if (this.hybridEvents) {
-        let target = this.target;
-        let view = target.ownerDocument ? target.ownerDocument.defaultView
-                                        : target;
-        view.addEventListener('click', this, true, true);
-      } else {
-        // We prevent end events to avoid sending a focus event. See bug 889717.
-        evt.preventDefault();
-      }
-    } else if (this.target && click && !this.panning) {
-      this.notify(this._activationTimer);
-    }
-
-    this._finishPanning();
-
-    // Now that we're done, avoid entraining the thing we just panned.
-    this.pointerDownTarget = null;
-  },
-
-  onTouchMove: function cp_onTouchMove(evt) {
-    if (!this.dragging)
-      return;
-
-    let screenX, screenY;
-    if (this.watchedEventsType == 'touch') {
-      let primaryTouch = this.findPrimaryPointer(evt.changedTouches);
-      if (evt.touches.length > 1 || !primaryTouch)
-        return;
-      screenX = primaryTouch.screenX;
-      screenY = primaryTouch.screenY;
-    } else {
-      screenX = evt.screenX;
-      screenY = evt.screenY;
-    }
-
-    let current = this.position;
-    let delta = new Point(screenX - current.x, screenY - current.y);
-    current.set(screenX, screenY);
-
-    KineticPanning.record(delta, evt.timeStamp);
-
-    let isPan = KineticPanning.isPan();
-
-    // If we've detected a pan gesture, cancel the active state of the
-    // current target.
-    if (!this.panning && isPan) {
-      this._resetActive();
-    }
-
-    // There's no possibility of us panning anything.
-    if (!this.scrollCallback) {
-      return;
-    }
-
-    // Scroll manually.
-    this.scrollCallback(delta.scale(-1));
-
-    if (!this.panning && isPan) {
-      this.panning = true;
-      this._activationTimer.cancel();
-    }
-
-    if (this.panning) {
-      // Only do this when we're actually executing a pan gesture.
-      // Otherwise synthetic mouse events will be canceled.
-      evt.stopPropagation();
-      evt.preventDefault();
-    }
-  },
-
-  // nsITimerCallback
-  notify: function cp_notify(timer) {
-    this._setActive(this.pointerDownTarget);
-  },
-
-  onKineticBegin: function cp_onKineticBegin(evt) {
-  },
-
-  onKineticPan: function cp_onKineticPan(delta) {
-    return !this.scrollCallback(delta);
-  },
-
-  onKineticEnd: function cp_onKineticEnd() {
-    if (!this.dragging)
-      this.scrollCallback = null;
-  },
-
-  getPannable: function cp_getPannable(node) {
-    let pannableNode = this._findPannable(node);
-    if (pannableNode) {
-      return [pannableNode, this._generateCallback(pannableNode)];
-    }
-
-    return [null, null];
-  },
-
-  _findPannable: function cp_findPannable(node) {
-    if (!(node instanceof Ci.nsIDOMHTMLElement) || node.tagName == 'HTML') {
-      return null;
-    }
-
-    let nodeContent = node.ownerDocument.defaultView;
-    while (!(node instanceof Ci.nsIDOMHTMLBodyElement)) {
-      let style = nodeContent.getComputedStyle(node, null);
-
-      let overflow = [style.getPropertyValue('overflow'),
-                      style.getPropertyValue('overflow-x'),
-                      style.getPropertyValue('overflow-y')];
-
-      let rect = node.getBoundingClientRect();
-      let isAuto = (overflow.indexOf('auto') != -1 &&
-                   (rect.height < node.scrollHeight ||
-                    rect.width < node.scrollWidth));
-
-      let isScroll = (overflow.indexOf('scroll') != -1);
-
-      let isScrollableTextarea = (node.tagName == 'TEXTAREA' &&
-          (node.scrollHeight > node.clientHeight ||
-           node.scrollWidth > node.clientWidth ||
-           ('scrollLeftMax' in node && node.scrollLeftMax > 0) ||
-           ('scrollTopMax' in node && node.scrollTopMax > 0)));
-      if (isScroll || isAuto || isScrollableTextarea) {
-        return node;
-      }
-
-      node = node.parentNode;
-    }
-
-    if (nodeContent.scrollMaxX || nodeContent.scrollMaxY) {
-      return nodeContent;
-    }
-
-    if (nodeContent.frameElement) {
-      return this._findPannable(nodeContent.frameElement);
-    }
-
-    return null;
-  },
-
-  _generateCallback: function cp_generateCallback(root) {
-    let firstScroll = true;
-    let target;
-    let current;
-    let win, doc, htmlNode, bodyNode;
-
-    function doScroll(node, delta) {
-      if (node instanceof Ci.nsIDOMHTMLElement) {
-        return node.scrollByNoFlush(delta.x, delta.y);
-      } else if (node instanceof Ci.nsIDOMWindow) {
-        win = node;
-        doc = win.document;
-
-        // "overflow:hidden" on either the <html> or the <body> node should
-        // prevent the user from scrolling the root viewport.
-        if (doc instanceof Ci.nsIDOMHTMLDocument) {
-          htmlNode = doc.documentElement;
-          bodyNode = doc.body;
-          if (win.getComputedStyle(htmlNode, null).overflowX == "hidden" ||
-              win.getComputedStyle(bodyNode, null).overflowX == "hidden") {
-            delta.x = 0;
-          }
-          if (win.getComputedStyle(htmlNode, null).overflowY == "hidden" ||
-              win.getComputedStyle(bodyNode, null).overflowY == "hidden") {
-            delta.y = 0;
-          }
-        }
-        let oldX = node.scrollX;
-        let oldY = node.scrollY;
-        node.scrollBy(delta.x, delta.y);
-        return (node.scrollX != oldX || node.scrollY != oldY);
-      }
-      // If we get here, |node| isn't an HTML element and it's not a window,
-      // but findPannable apparently thought it was scrollable... What is it?
-      return false;
-    }
-
-    function targetParent(node) {
-      return node.parentNode || node.frameElement || null;
-    }
-
-    function scroll(delta) {
-      current = root;
-      firstScroll = true;
-      while (current) {
-        if (doScroll(current, delta)) {
-          firstScroll = false;
-          return true;
-        }
-
-        // TODO The current code looks for possible scrolling regions only if
-        // this is the first scroll action but this should be more dynamic.
-        if (!firstScroll) {
-          return false;
-        }
-
-        current = ContentPanningAPZDisabled._findPannable(targetParent(current));
-      }
-
-      // There is nothing scrollable here.
-      return false;
-    }
-    return scroll;
-  },
-
-  get _activationTimer() {
-    delete this._activationTimer;
-    return this._activationTimer = Cc["@mozilla.org/timer;1"]
-                                     .createInstance(Ci.nsITimer);
-  },
-
-  get _activationDelayMs() {
-    let delay = Services.prefs.getIntPref('ui.touch_activation.delay_ms');
-    delete this._activationDelayMs;
-    return this._activationDelayMs = delay;
-  },
-
-  get _domUtils() {
-    delete this._domUtils;
-    return this._domUtils = Cc['@mozilla.org/inspector/dom-utils;1']
-                              .getService(Ci.inIDOMUtils);
-  },
-
-  _resetActive: function cp_resetActive() {
-    let elt = this.pointerDownTarget || this.target;
-    let root = elt.ownerDocument || elt.document;
-    this._setActive(root.documentElement);
-  },
-
-  _setActive: function cp_setActive(elt) {
-    const kStateActive = 0x00000001;
-    this._domUtils.setContentState(elt, kStateActive);
-  },
-
-  _finishPanning: function() {
-    this.dragging = false;
-    delete this.primaryPointerId;
-    this._activationTimer.cancel();
-
-    // If there is a scroll action, let's do a manual kinetic panning action.
-    if (this.panning) {
-      KineticPanning.start(this);
-    }
-  },
-};
-
-// Min/max velocity of kinetic panning. This is in pixels/millisecond.
-const kMinVelocity = 0.2;
-const kMaxVelocity = 6;
-
-// Constants that affect the "friction" of the scroll pane.
-const kExponentialC = 1000;
-const kPolynomialC = 100 / 1000000;
-
-// How often do we change the position of the scroll pane?
-// Too often and panning may jerk near the end.
-// Too little and panning will be choppy. In milliseconds.
-const kUpdateInterval = 16;
-
-// The numbers of momentums to use for calculating the velocity of the pan.
-// Those are taken from the end of the action
-const kSamples = 5;
-
-const KineticPanning = {
-  _position: new Point(0, 0),
-  _velocity: new Point(0, 0),
-  _acceleration: new Point(0, 0),
-
-  get active() {
-    return this.target !== null;
-  },
-
-  target: null,
-  start: function kp_start(target) {
-    this.target = target;
-
-    // Calculate the initial velocity of the movement based on user input
-    let momentums = this.momentums;
-    let flick = momentums[momentums.length - 1].time - momentums[0].time < 300;
-
-    let distance = new Point(0, 0);
-    momentums.forEach(function(momentum) {
-      distance.add(momentum.dx, momentum.dy);
-    });
-
-    function clampFromZero(x, min, max) {
-      if (x >= 0)
-        return Math.max(min, Math.min(max, x));
-      return Math.min(-min, Math.max(-max, x));
-    }
-
-    let elapsed = momentums[momentums.length - 1].time - momentums[0].time;
-    let velocityX = clampFromZero(distance.x / elapsed, 0, kMaxVelocity);
-    let velocityY = clampFromZero(distance.y / elapsed, 0, kMaxVelocity);
-
-    let velocity = this._velocity;
-    if (flick) {
-      // Very fast pan action that does not generate a click are very often pan
-      // action. If this is a small gesture then it will not move the view a lot
-      // and so it will be above the minimun threshold and not generate any
-      // kinetic panning. This does not look on a device since this is often
-      // a real gesture, so let's lower the velocity threshold for such moves.
-      velocity.set(velocityX, velocityY);
-    } else {
-      velocity.set(Math.abs(velocityX) < kMinVelocity ? 0 : velocityX,
-                   Math.abs(velocityY) < kMinVelocity ? 0 : velocityY);
-    }
-    this.momentums = [];
-
-    // Set acceleration vector to opposite signs of velocity
-    function sign(x) {
-      return x ? (x > 0 ? 1 : -1) : 0;
-    }
-
-    this._acceleration.set(velocity.clone().map(sign).scale(-kPolynomialC));
-
-    // Reset the position
-    this._position.set(0, 0);
-
-    this._startAnimation();
-
-    this.target.onKineticBegin();
-  },
-
-  stop: function kp_stop() {
-    this.reset();
-
-    if (!this.target)
-      return;
-
-    this.target.onKineticEnd();
-    this.target = null;
-  },
-
-  reset: function kp_reset() {
-    this.momentums = [];
-    this.distance.set(0, 0);
-  },
-
-  momentums: [],
-  record: function kp_record(delta, timestamp) {
-    this.momentums.push({ 'time': this._getTime(timestamp),
-                          'dx' : delta.x, 'dy' : delta.y });
-
-    // We only need to keep kSamples in this.momentums.
-    if (this.momentums.length > kSamples) {
-      this.momentums.shift();
-    }
-
-    this.distance.add(delta.x, delta.y);
-  },
-
-  _getTime: function kp_getTime(time) {
-    // Touch events generated by the platform or hand-made are defined in
-    // microseconds instead of milliseconds. Bug 77992 will fix this at the
-    // platform level.
-    if (time > Date.now()) {
-      return Math.floor(time / 1000);
-    } else {
-      return time;
-    }
-  },
-
-  get threshold() {
-    let dpi = content.QueryInterface(Ci.nsIInterfaceRequestor)
-                     .getInterface(Ci.nsIDOMWindowUtils)
-                     .displayDPI;
-
-    let threshold = Services.prefs.getIntPref('ui.dragThresholdX') / 240 * dpi;
-
-    delete this.threshold;
-    return this.threshold = threshold;
-  },
-
-  distance: new Point(0, 0),
-  isPan: function cp_isPan() {
-    return (Math.abs(this.distance.x) > this.threshold ||
-            Math.abs(this.distance.y) > this.threshold);
-  },
-
-  _startAnimation: function kp_startAnimation() {
-    let c = kExponentialC;
-    function getNextPosition(position, v, a, t) {
-      // Important traits for this function:
-      //   p(t=0) is 0
-      //   p'(t=0) is v0
-      //
-      // We use exponential to get a smoother stop, but by itself exponential
-      // is too smooth at the end. Adding a polynomial with the appropriate
-      // weight helps to balance
-      position.set(v.x * Math.exp(-t / c) * -c + a.x * t * t + v.x * c,
-                   v.y * Math.exp(-t / c) * -c + a.y * t * t + v.y * c);
-    }
-
-    let startTime = content.mozAnimationStartTime;
-    let elapsedTime = 0, targetedTime = 0, averageTime = 0;
-
-    let velocity = this._velocity;
-    let acceleration = this._acceleration;
-
-    let position = this._position;
-    let nextPosition = new Point(0, 0);
-    let delta = new Point(0, 0);
-
-    let callback = (function(timestamp) {
-      if (!this.target)
-        return;
-
-      // To make animation end fast enough but to keep smoothness, average the
-      // ideal time frame (smooth animation) with the actual time lapse
-      // (end fast enough).
-      // Animation will never take longer than 2 times the ideal length of time.
-      elapsedTime = timestamp - startTime;
-      targetedTime += kUpdateInterval;
-      averageTime = (targetedTime + elapsedTime) / 2;
-
-      // Calculate new position.
-      getNextPosition(nextPosition, velocity, acceleration, averageTime);
-      delta.set(Math.round(nextPosition.x - position.x),
-                Math.round(nextPosition.y - position.y));
-
-      // Test to see if movement is finished for each component.
-      if (delta.x * acceleration.x > 0)
-        delta.x = position.x = velocity.x = acceleration.x = 0;
-
-      if (delta.y * acceleration.y > 0)
-        delta.y = position.y = velocity.y = acceleration.y = 0;
-
-      if (velocity.equals(0, 0) || delta.equals(0, 0)) {
-        this.stop();
-        return;
-      }
-
-      position.add(delta);
-      if (this.target.onKineticPan(delta.scale(-1))) {
-        this.stop();
-        return;
-      }
-
-      content.mozRequestAnimationFrame(callback);
-    }).bind(this);
-
-    content.mozRequestAnimationFrame(callback);
-  }
-};
diff --git a/dom/ipc/jar.mn b/dom/ipc/jar.mn
index c1d6647af2e6..07297f4f69be 100644
--- a/dom/ipc/jar.mn
+++ b/dom/ipc/jar.mn
@@ -8,6 +8,5 @@ toolkit.jar:
         content/global/BrowserElementChild.js (../browser-element/BrowserElementChild.js)
         content/global/BrowserElementChildPreload.js (../browser-element/BrowserElementChildPreload.js)
 *       content/global/BrowserElementPanning.js (../browser-element/BrowserElementPanning.js)
-*       content/global/BrowserElementPanningAPZDisabled.js (../browser-element/BrowserElementPanningAPZDisabled.js)
         content/global/preload.js (preload.js)
         content/global/post-fork-preload.js (post-fork-preload.js)
diff --git a/dom/ipc/preload.js b/dom/ipc/preload.js
index de0cfd95d8f5..a897c3f5edea 100644
--- a/dom/ipc/preload.js
+++ b/dom/ipc/preload.js
@@ -91,13 +91,6 @@ const BrowserElementIsPreloaded = true;
   } catch (e) {
   }
 
-  try {
-    if (Services.prefs.getBoolPref("layers.async-pan-zoom.enabled") === false) {
-      Services.scriptloader.loadSubScript("chrome://global/content/BrowserElementPanningAPZDisabled.js", global);
-    }
-  } catch (e) {
-  }
-
   Services.scriptloader.loadSubScript("chrome://global/content/BrowserElementPanning.js", global);
   Services.scriptloader.loadSubScript("chrome://global/content/BrowserElementChildPreload.js", global);