--- a/browser/components/customizableui/content/panelUI.js
+++ b/browser/components/customizableui/content/panelUI.js
@@ -55,17 +55,29 @@ const PanelUI = {
 
     this.menuButton.addEventListener("mousedown", this);
     this.menuButton.addEventListener("keypress", this);
     this._overlayScrollListenerBoundFn = this._overlayScrollListener.bind(this);
 
     Services.obs.addObserver(this, "fullscreen-nav-toolbox");
     Services.obs.addObserver(this, "appMenu-notifications");
 
-    window.addEventListener("fullscreen", this);
+    Services.prefs.addObserver("browser.fullscreen.autohide", this);
+
+    // On OSX, or with autohide preffed off, MozDOMFullscreen is the only
+    // event we care about, since fullscreen should behave just like non
+    // fullscreen. Otherwise, we don't want to listen to these because
+    // we'd just be spamming ourselves with both of them whenever a user
+    // opened a video.
+    if (this.autoHideToolbarInFullScreen) {
+      window.addEventListener("fullscreen", this);
+    } else {
+      window.addEventListener("MozDOMFullscreen:Entered", this);
+      window.addEventListener("MozDOMFullscreen:Exited", this);
+    }
     window.addEventListener("activate", this);
     window.matchMedia("(-moz-overlay-scrollbars)").addListener(this._overlayScrollListenerBoundFn);
     CustomizableUI.addListener(this);
 
     for (let event of this.kEvents) {
       this.notificationPanel.addEventListener(event, this);
     }
 
@@ -170,16 +182,20 @@ const PanelUI = {
     this._removeEventListeners();
     for (let event of this.kEvents) {
       this.notificationPanel.removeEventListener(event, this);
     }
 
     Services.obs.removeObserver(this, "fullscreen-nav-toolbox");
     Services.obs.removeObserver(this, "appMenu-notifications");
 
+    Services.prefs.removeObserver("browser.fullscreen.autohide", this);
+
+    window.removeEventListener("MozDOMFullscreen:Entered", this);
+    window.removeEventListener("MozDOMFullscreen:Exited", this);
     window.removeEventListener("fullscreen", this);
     window.removeEventListener("activate", this);
     this.menuButton.removeEventListener("mousedown", this);
     this.menuButton.removeEventListener("keypress", this);
     window.matchMedia("(-moz-overlay-scrollbars)").removeListener(this._overlayScrollListenerBoundFn);
     CustomizableUI.removeListener(this);
     this._overlayScrollListenerBoundFn = null;
   },
@@ -283,16 +299,31 @@ const PanelUI = {
       case "appMenu-notifications":
         // Don't initialize twice.
         if (status == "init" && this._notifications) {
           break;
         }
         this._notifications = AppMenuNotifications.notifications;
         this._updateNotifications(true);
         break;
+      case "nsPref:changed":
+        if (status == "browser.fullscreen.autohide") {
+          if (this.autoHideToolbarInFullScreen) {
+            window.removeEventListener("MozDOMFullscreen:Entered", this);
+            window.removeEventListener("MozDOMFullscreen:Exited", this);
+            window.addEventListener("fullscreen", this);
+          } else {
+            window.addEventListener("MozDOMFullscreen:Entered", this);
+            window.addEventListener("MozDOMFullscreen:Exited", this);
+            window.removeEventListener("fullscreen", this);
+          }
+
+          this._updateNotifications(false);
+        }
+        break;
     }
   },
 
   handleEvent(aEvent) {
     // Ignore context menus and menu button menus showing and hiding:
     if (aEvent.type.startsWith("popup") &&
         aEvent.target != this.panel) {
       return;
@@ -321,16 +352,18 @@ const PanelUI = {
         break;
       case "mousedown":
         if (aEvent.button == 0)
           this.toggle(aEvent);
         break;
       case "keypress":
         this.toggle(aEvent);
         break;
+      case "MozDOMFullscreen:Entered":
+      case "MozDOMFullscreen:Exited":
       case "fullscreen":
       case "activate":
         this._updateNotifications();
         break;
     }
   },
 
   get isReady() {
@@ -338,16 +371,21 @@ const PanelUI = {
   },
 
   get isNotificationPanelOpen() {
     let panelState = this.notificationPanel.state;
 
     return panelState == "showing" || panelState == "open";
   },
 
+  get autoHideToolbarInFullScreen() {
+    return Services.prefs.getBoolPref("browser.fullscreen.autohide", false) &&
+           Services.appinfo.OS !== "Darwin";
+  },
+
   /**
    * Registering the menu panel is done lazily for performance reasons. This
    * method is exposed so that CustomizationMode can force panel-readyness in the
    * event that customization mode is started before the panel has been opened
    * by the user.
    *
    * @param aCustomizing (optional) set to true if this was called while entering
    *        customization mode. If that's the case, we trust that customization
@@ -739,20 +777,18 @@ const PanelUI = {
       // since we don't want their doorhangers competing for attention
       doorhangers.forEach(n => { n.dismissed = true; })
       this._hidePopup();
       this._clearBadge();
       if (!notifications[0].options.badgeOnly) {
         this._showBannerItem(notifications[0]);
       }
     } else if (doorhangers.length > 0) {
-      let autoHideFullScreen = Services.prefs.getBoolPref("browser.fullscreen.autohide", false) &&
-                               Services.appinfo.OS !== "Darwin";
       // Only show the doorhanger if the window is focused and not fullscreen
-      if ((window.fullScreen && autoHideFullScreen) || Services.focus.activeWindow !== window) {
+      if ((window.fullScreen && this.autoHideToolbarInFullScreen) || Services.focus.activeWindow !== window) {
         this._hidePopup();
         this._showBadge(doorhangers[0]);
         this._showBannerItem(doorhangers[0]);
       } else {
         this._clearBadge();
         this._showNotificationPanel(doorhangers[0]);
       }
     } else {