--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -69,17 +69,16 @@ Cu.import("resource://gre/modules/XPCOMU
 const nsIWebNavigation = Ci.nsIWebNavigation;
 
 var gCharsetMenu = null;
 var gLastBrowserCharset = null;
 var gPrevCharset = null;
 var gProxyFavIcon = null;
 var gLastValidURLStr = "";
 var gProgressCollapseTimer = null;
-var appCore = null;
 var gSidebarCommand = "";
 var gInPrintPreviewMode = false;
 let gDownloadMgr = null;
 
 // Global variable that holds the nsContextMenu instance.
 var gContextMenu = null;
 
 var gChromeState = null; // chrome state before we went into print preview
@@ -916,20 +915,16 @@ function BrowserStartup() {
   if ("arguments" in window && window.arguments[0])
     uriToLoad = window.arguments[0];
 
   var isLoadingBlank = uriToLoad == "about:blank";
   var mustLoadSidebar = false;
 
   prepareForStartup();
 
-#ifdef ENABLE_PAGE_CYCLER
-  appCore.startPageCycler();
-#else
-# only load url passed in when we're not page cycling
   if (uriToLoad && !isLoadingBlank) { 
     if (uriToLoad instanceof Ci.nsISupportsArray) {
       let count = uriToLoad.Count();
       let specs = [];
       for (let i = 0; i < count; i++) {
         let urisstring = uriToLoad.GetElementAt(i).QueryInterface(Ci.nsISupportsString);
         specs.push(urisstring.data);
       }
@@ -956,17 +951,16 @@ function BrowserStartup() {
               window.arguments[4] || false);
       content.focus();
     }
     // Note: loadOneOrMoreURIs *must not* be called if window.arguments.length >= 3.
     // Such callers expect that window.arguments[0] is handled as a single URI.
     else
       loadOneOrMoreURIs(uriToLoad);
   }
-#endif
 
   if (window.opener && !window.opener.closed) {
     let openerFindBar = window.opener.gFindBar;
     if (openerFindBar && !openerFindBar.hidden &&
         openerFindBar.findMode == gFindBar.FIND_NORMAL)
       gFindBar.open();
 
     let openerSidebarBox = window.opener.document.getElementById("sidebar-box");
@@ -1101,22 +1095,16 @@ function prepareForStartup() {
   gBrowser.addEventListener("PluginBlocklisted", gMissingPluginInstaller.newMissingPlugin, true, true);
   gBrowser.addEventListener("PluginDisabled", gMissingPluginInstaller.newDisabledPlugin, true, true);
   gBrowser.addEventListener("NewPluginInstalled", gMissingPluginInstaller.refreshBrowser, false);
   gBrowser.addEventListener("NewTab", BrowserOpenTab, false);
   window.addEventListener("AppCommand", HandleAppCommandEvent, true);
 
   var webNavigation;
   try {
-    // Create the browser instance component.
-    appCore = Components.classes["@mozilla.org/appshell/component/browser/instance;1"]
-                        .createInstance(Components.interfaces.nsIBrowserInstance);
-    if (!appCore)
-      throw "couldn't create a browser instance";
-
     webNavigation = getWebNavigation();
     if (!webNavigation)
       throw "no XBL binding for browser";
   } catch (e) {
     alert("Error launching browser window:" + e);
     window.close(); // Give up.
     return;
   }
@@ -1139,19 +1127,16 @@ function prepareForStartup() {
       var arrayArgComponents = window.arguments[1].split("=");
       if (arrayArgComponents) {
         //we should "inherit" the charset menu setting in a new window
         getMarkupDocumentViewer().defaultCharacterSet = arrayArgComponents[1];
       }
     }
   }
 
-  // Initialize browser instance..
-  appCore.setWebShellWindow(window);
-
   // Manually hook up session and global history for the first browser
   // so that we don't have to load global history before bringing up a
   // window.
   // Wire up session and global history before any possible
   // progress notifications for back/forward button updating
   webNavigation.sessionHistory = Components.classes["@mozilla.org/browser/shistory;1"]
                                            .createInstance(Components.interfaces.nsISHistory);
   var os = Components.classes["@mozilla.org/observer-service;1"].getService(Components.interfaces.nsIObserverService);
@@ -1429,20 +1414,16 @@ function BrowserShutdown()
   window.XULBrowserWindow = null;
   window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
         .getInterface(Components.interfaces.nsIWebNavigation)
         .QueryInterface(Components.interfaces.nsIDocShellTreeItem).treeOwner
         .QueryInterface(Components.interfaces.nsIInterfaceRequestor)
         .getInterface(Components.interfaces.nsIXULWindow)
         .XULBrowserWindow = null;
   window.QueryInterface(Ci.nsIDOMChromeWindow).browserDOMWindow = null;
-
-  // Close the app core.
-  if (appCore)
-    appCore.close();
 }
 
 #ifdef XP_MACOSX
 // nonBrowserWindowStartup(), nonBrowserWindowDelayedStartup(), and
 // nonBrowserWindowShutdown() are used for non-browser windows in
 // macBrowserOverlay
 function nonBrowserWindowStartup()
 {