--- a/browser/base/content/browser-fullScreenAndPointerLock.js
+++ b/browser/base/content/browser-fullScreenAndPointerLock.js
@@ -586,17 +586,17 @@ var FullScreen = {
     gNavToolbox.style.marginTop = "";
 
     if (!this._isChromeCollapsed) {
       return;
     }
 
     // Track whether mouse is near the toolbox
     if (trackMouse && !this.useLionFullScreen) {
-      let rect = gBrowser.mPanelContainer.getBoundingClientRect();
+      let rect = gBrowser.tabpanels.getBoundingClientRect();
       this._mouseTargetRect = {
         top: rect.top + 50,
         bottom: rect.bottom,
         left: rect.left,
         right: rect.right
       };
       MousePosTracker.addListener(this);
     }

--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -1316,17 +1316,17 @@ var gBrowserInit = {
     mm.loadFrameScript("chrome://browser/content/content-UITour.js", true);
     mm.loadFrameScript("chrome://global/content/content-HybridContentTelemetry.js", true);
     mm.loadFrameScript("chrome://global/content/manifestMessages.js", true);
 
     window.messageManager.addMessageListener("Browser:LoadURI", RedirectLoad);
 
     if (!gMultiProcessBrowser) {
       // There is a Content:Click message manually sent from content.
-      Services.els.addSystemEventListener(gBrowser.mPanelContainer, "click",
+      Services.els.addSystemEventListener(gBrowser.tabpanels, "click",
         contentAreaClick, true);
     }
 
     // hook up UI through progress listener
     gBrowser.addProgressListener(window.XULBrowserWindow);
     gBrowser.addTabsProgressListener(window.TabsProgressListener);
 
     SidebarUI.init();

--- a/browser/base/content/tabbrowser.js
+++ b/browser/base/content/tabbrowser.js
@@ -23,32 +23,32 @@ window._gBrowser = {
       Services.els.addSystemEventListener(document, "keypress", this, false);
     }
     window.addEventListener("sizemodechange", this);
     window.addEventListener("occlusionstatechange", this);
 
     this._setupInitialBrowserAndTab();
 
     if (Services.prefs.getBoolPref("browser.display.use_system_colors")) {
-      this.mPanelContainer.style.backgroundColor = "-moz-default-background-color";
+      this.tabpanels.style.backgroundColor = "-moz-default-background-color";
     } else if (Services.prefs.getIntPref("browser.display.document_color_use") == 2) {
-      this.mPanelContainer.style.backgroundColor =
+      this.tabpanels.style.backgroundColor =
         Services.prefs.getCharPref("browser.display.background_color");
     }
 
     let messageManager = window.getGroupMessageManager("browsers");
     if (gMultiProcessBrowser) {
       messageManager.addMessageListener("DOMTitleChanged", this);
       messageManager.addMessageListener("DOMWindowClose", this);
       window.messageManager.addMessageListener("contextmenu", this);
       messageManager.addMessageListener("Browser:Init", this);
 
       // If this window has remote tabs, switch to our tabpanels fork
       // which does asynchronous tab switching.
-      this.mPanelContainer.classList.add("tabbrowser-tabpanels");
+      this.tabpanels.classList.add("tabbrowser-tabpanels");
     } else {
       this._outerWindowIDBrowserMap.set(this.selectedBrowser.outerWindowID,
         this.selectedBrowser);
     }
     messageManager.addMessageListener("DOMWindowFocus", this);
     messageManager.addMessageListener("RefreshBlocker:Blocked", this);
     messageManager.addMessageListener("Browser:WindowCreated", this);
 
@@ -194,34 +194,34 @@ window._gBrowser = {
     return this.tabs = this.tabContainer.childNodes;
   },
 
   get tabbox() {
     delete this.tabbox;
     return this.tabbox = document.getElementById("tabbrowser-tabbox");
   },
 
-  get mPanelContainer() {
-    delete this.mPanelContainer;
-    return this.mPanelContainer = document.getElementById("tabbrowser-tabpanels");
+  get tabpanels() {
+    delete this.tabpanels;
+    return this.tabpanels = document.getElementById("tabbrowser-tabpanels");
   },
 
   get addEventListener() {
     delete this.addEventListener;
-    return this.addEventListener = this.mPanelContainer.addEventListener.bind(this.mPanelContainer);
+    return this.addEventListener = this.tabpanels.addEventListener.bind(this.tabpanels);
   },
 
   get removeEventListener() {
     delete this.removeEventListener;
-    return this.removeEventListener = this.mPanelContainer.removeEventListener.bind(this.mPanelContainer);
+    return this.removeEventListener = this.tabpanels.removeEventListener.bind(this.tabpanels);
   },
 
   get dispatchEvent() {
     delete this.dispatchEvent;
-    return this.dispatchEvent = this.mPanelContainer.dispatchEvent.bind(this.mPanelContainer);
+    return this.dispatchEvent = this.tabpanels.dispatchEvent.bind(this.tabpanels);
   },
 
   get visibleTabs() {
     if (!this._visibleTabs)
       this._visibleTabs = Array.filter(this.tabs,
         tab => !tab.hidden && !tab.closing);
     return this._visibleTabs;
   },
@@ -294,17 +294,17 @@ window._gBrowser = {
     for (let attribute in this._defaultBrowserAttributes) {
       this._defaultBrowserAttributes[attribute] = browser.getAttribute(attribute);
     }
 
     let tab = this.tabs[0];
     this._selectedTab = tab;
 
     let uniqueId = this._generateUniquePanelID();
-    this.mPanelContainer.childNodes[0].id = uniqueId;
+    this.tabpanels.childNodes[0].id = uniqueId;
     tab.linkedPanel = uniqueId;
     tab.permanentKey = browser.permanentKey;
     tab._tPos = 0;
     tab._fullyOpen = true;
     tab.linkedBrowser = browser;
     this._tabForBrowser.set(browser, tab);
 
     // Hook the browser up with a progress listener.
@@ -1795,17 +1795,17 @@ window._gBrowser = {
 
     let remoteType =
       E10SUtils.getRemoteTypeForURI(BROWSER_NEW_TAB_URL,
         gMultiProcessBrowser);
     let browser = this._createBrowser({ isPreloadBrowser: true, remoteType });
     this._preloadedBrowser = browser;
 
     let notificationbox = this.getNotificationBox(browser);
-    this.mPanelContainer.appendChild(notificationbox);
+    this.tabpanels.appendChild(notificationbox);
 
     if (remoteType != E10SUtils.NOT_REMOTE) {
       // For remote browsers, we need to make sure that the webProgress is
       // instantiated, otherwise the parent won't get informed about the state
       // of the preloaded browser until it gets attached to a tab.
       browser.webProgress;
     }
 
@@ -2050,17 +2050,17 @@ window._gBrowser = {
 
     // Inject the <browser> into the DOM if necessary.
     if (!notificationbox.parentNode) {
       // NB: this appendChild call causes us to run constructors for the
       // browser element, which fires off a bunch of notifications. Some
       // of those notifications can cause code to run that inspects our
       // state, so it is important that the tab element is fully
       // initialized by this point.
-      this.mPanelContainer.appendChild(notificationbox);
+      this.tabpanels.appendChild(notificationbox);
     }
 
     // wire up a progress listener for the new browser object.
     let tabListener = new TabProgressListener(aTab, browser, uriIsAboutBlank, usingPreloadedContent);
     const filter = Cc["@mozilla.org/appshell/component/browser-status-filter;1"]
       .createInstance(Ci.nsIWebProgress);
     filter.addProgressListener(tabListener, Ci.nsIWebProgress.NOTIFY_ALL);
     browser.webProgress.addProgressListener(filter, Ci.nsIWebProgress.NOTIFY_ALL);
@@ -2141,17 +2141,17 @@ window._gBrowser = {
       tab._findBar.close(true);
       tab._findBar.remove();
       delete tab._findBar;
     }
 
     aBrowser.destroy();
 
     let notificationbox = this.getNotificationBox(aBrowser);
-    this.mPanelContainer.removeChild(notificationbox);
+    this.tabpanels.removeChild(notificationbox);
     tab.removeAttribute("linkedpanel");
 
     this._createLazyBrowser(tab);
 
     let evt = new CustomEvent("TabBrowserDiscarded", { bubbles: true });
     tab.dispatchEvent(evt);
   },
 

--- a/browser/modules/AsyncTabSwitcher.jsm
+++ b/browser/modules/AsyncTabSwitcher.jsm
@@ -383,39 +383,39 @@ class AsyncTabSwitcher {
 
     // Show or hide the spinner as needed.
     let needSpinner = this.getTabState(showTab) != this.STATE_LOADED &&
                       !this.minimizedOrFullyOccluded &&
                       !shouldBeBlank;
 
     if (!needSpinner && this.spinnerTab) {
       this.spinnerHidden();
-      this.tabbrowser.mPanelContainer.removeAttribute("pendingpaint");
+      this.tabbrowser.tabpanels.removeAttribute("pendingpaint");
       this.spinnerTab.linkedBrowser.removeAttribute("pendingpaint");
       this.spinnerTab = null;
     } else if (needSpinner && this.spinnerTab !== showTab) {
       if (this.spinnerTab) {
         this.spinnerTab.linkedBrowser.removeAttribute("pendingpaint");
       } else {
         this.spinnerDisplayed();
       }
       this.spinnerTab = showTab;
-      this.tabbrowser.mPanelContainer.setAttribute("pendingpaint", "true");
+      this.tabbrowser.tabpanels.setAttribute("pendingpaint", "true");
       this.spinnerTab.linkedBrowser.setAttribute("pendingpaint", "true");
     }
 
     // Switch to the tab we've decided to make visible.
     if (this.visibleTab !== showTab) {
       this.tabbrowser._adjustFocusBeforeTabSwitch(this.visibleTab, showTab);
       this.visibleTab = showTab;
 
       this.maybeVisibleTabs.add(showTab);
 
       let tabs = this.tabbrowser.tabbox.tabs;
-      let tabPanel = this.tabbrowser.mPanelContainer;
+      let tabPanel = this.tabbrowser.tabpanels;
       let showPanel = tabs.getRelatedElement(showTab);
       let index = Array.indexOf(tabPanel.childNodes, showPanel);
       if (index != -1) {
         this.log(`Switch to tab ${index} - ${this.tinfo(showTab)}`);
         tabPanel.setAttribute("selectedIndex", index);
         if (showTab === this.requestedTab) {
           if (this._requestingTab) {
             /*