--- a/browser/base/content/browser-fxaccounts.js
+++ b/browser/base/content/browser-fxaccounts.js
@@ -2,16 +2,17 @@
 # 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/.
 
 XPCOMUtils.defineLazyGetter(this, "FxAccountsCommon", function () {
   return Cu.import("resource://gre/modules/FxAccountsCommon.js", {});
 });
 
 const PREF_SYNC_START_DOORHANGER = "services.sync.ui.showSyncStartDoorhanger";
+const DOORHANGER_ACTIVATE_DELAY_MS = 5000;
 
 let gFxAccounts = {
 
   _initialized: false,
   _inCustomizationMode: false,
 
   get weave() {
     delete this.weave;
@@ -28,26 +29,16 @@ let gFxAccounts = {
       "weave:service:sync:start",
       "weave:service:login:error",
       "weave:service:setup-complete",
       FxAccountsCommon.ONVERIFIED_NOTIFICATION,
       FxAccountsCommon.ONLOGOUT_NOTIFICATION
     ];
   },
 
-  // The set of topics that only the active window should handle.
-  get activeWindowTopics() {
-    // Do all this dance to lazy-load FxAccountsCommon.
-    delete this.activeWindowTopics;
-    return this.activeWindowTopics = new Set([
-      "weave:service:sync:start",
-      FxAccountsCommon.ONVERIFIED_NOTIFICATION
-    ]);
-  },
-
   get button() {
     delete this.button;
     return this.button = document.getElementById("PanelUI-fxa-status");
   },
 
   get loginFailed() {
     // Referencing Weave.Service will implicitly initialize sync, and we don't
     // want to force that - so first check if it is ready.
@@ -59,31 +50,31 @@ let gFxAccounts = {
     }
     // LOGIN_FAILED_LOGIN_REJECTED explicitly means "you must log back in".
     // All other login failures are assumed to be transient and should go
     // away by themselves, so aren't reflected here.
     return Weave.Status.login == Weave.LOGIN_FAILED_LOGIN_REJECTED;
   },
 
   get isActiveWindow() {
-    let mostRecentNonPopupWindow =
-      RecentWindow.getMostRecentBrowserWindow({allowPopups: false});
-    return window == mostRecentNonPopupWindow;
+    let fm = Cc["@mozilla.org/focus-manager;1"].getService(Ci.nsIFocusManager);
+    return fm.activeWindow == window;
   },
 
   init: function () {
     // Bail out if we're already initialized and for pop-up windows.
     if (this._initialized || !window.toolbar.visible) {
       return;
     }
 
     for (let topic of this.topics) {
       Services.obs.addObserver(this, topic, false);
     }
 
+    addEventListener("activate", this);
     gNavToolbox.addEventListener("customizationstarting", this);
     gNavToolbox.addEventListener("customizationending", this);
 
     this._initialized = true;
 
     this.updateUI();
   },
 
@@ -95,50 +86,58 @@ let gFxAccounts = {
     for (let topic of this.topics) {
       Services.obs.removeObserver(this, topic);
     }
 
     this._initialized = false;
   },
 
   observe: function (subject, topic) {
-    // Ignore certain topics if we're not the active window.
-    if (this.activeWindowTopics.has(topic) && !this.isActiveWindow) {
-      return;
-    }
-
     switch (topic) {
       case FxAccountsCommon.ONVERIFIED_NOTIFICATION:
         Services.prefs.setBoolPref(PREF_SYNC_START_DOORHANGER, true);
         break;
       case "weave:service:sync:start":
         this.onSyncStart();
         break;
       default:
         this.updateUI();
         break;
     }
   },
 
   onSyncStart: function () {
+    if (!this.isActiveWindow) {
+      return;
+    }
+
     let showDoorhanger = false;
 
     try {
       showDoorhanger = Services.prefs.getBoolPref(PREF_SYNC_START_DOORHANGER);
     } catch (e) { /* The pref might not exist. */ }
 
     if (showDoorhanger) {
       Services.prefs.clearUserPref(PREF_SYNC_START_DOORHANGER);
       this.showSyncStartedDoorhanger();
     }
   },
 
   handleEvent: function (event) {
-    this._inCustomizationMode = event.type == "customizationstarting";
-    this.updateUI();
+    if (event.type == "activate") {
+      // Our window might have been in the background while we received the
+      // sync:start notification. If still needed, show the doorhanger after
+      // a short delay. Without this delay the doorhanger would not show up
+      // or with a too small delay show up while we're still animating the
+      // window.
+      setTimeout(() => this.onSyncStart(), DOORHANGER_ACTIVATE_DELAY_MS);
+    } else {
+      this._inCustomizationMode = event.type == "customizationstarting";
+      this.updateUI();
+    }
   },
 
   showDoorhanger: function (id) {
     let panel = document.getElementById(id);
     let anchor = document.getElementById("PanelUI-menu-button");
 
     let iconAnchor =
       document.getAnonymousElementByAttribute(anchor, "class",