--- a/browser/base/content/browser-tabsintitlebar.js
+++ b/browser/base/content/browser-tabsintitlebar.js
@@ -3,19 +3,16 @@
  * 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/. */
 
 // Note: the file browser-tabsintitlebar-stub.js is used instead of
 // this one on platforms which don't have CAN_DRAW_IN_TITLEBAR defined.
 
 var TabsInTitlebar = {
   init() {
-    if (this._initialized) {
-      return;
-    }
     this._readPref();
     Services.prefs.addObserver(this._prefName, this);
 
     // Always disable on unsupported GTK versions.
     if (AppConstants.MOZ_WIDGET_TOOLKIT == "gtk3") {
       this.allowedBy("gtk", window.matchMedia("(-moz-gtk-csd-available)"));
     }
 
@@ -41,17 +38,17 @@ var TabsInTitlebar = {
       if (aArea == CustomizableUI.AREA_TABSTRIP || aArea == CustomizableUI.AREA_MENUBAR)
         this._update(true);
     };
     CustomizableUI.addListener(this);
 
     addEventListener("resolutionchange", this, false);
 
     this._initialized = true;
-    this._update();
+    this._update(true, true);
   },
 
   allowedBy(condition, allow) {
     if (allow) {
       if (condition in this._disallowed) {
         delete this._disallowed[condition];
         this._update(true);
       }
@@ -75,46 +72,55 @@ var TabsInTitlebar = {
   },
 
   handleEvent(aEvent) {
     if (aEvent.type == "resolutionchange" && aEvent.target == window) {
       this._update(true);
     }
   },
 
+  onDOMContentLoaded() {
+    this._domLoaded = true;
+    this._update(true);
+  },
+
   _onMenuMutate(aMutations) {
     for (let mutation of aMutations) {
       if (mutation.attributeName == "inactive" ||
           mutation.attributeName == "autohide") {
         TabsInTitlebar._update(true);
         return;
       }
     }
   },
 
   _initialized: false,
   _disallowed: {},
   _prefName: "browser.tabs.drawInTitlebar",
   _lastSizeMode: null,
+  _domLoaded: false,
 
   _readPref() {
     this.allowedBy("pref",
                    Services.prefs.getBoolPref(this._prefName));
   },
 
-  _update(aForce = false) {
+  _update(aForce = false, aFromInit = false) {
     let $ = id => document.getElementById(id);
     let rect = ele => ele.getBoundingClientRect();
     let verticalMargins = cstyle => parseFloat(cstyle.marginBottom) + parseFloat(cstyle.marginTop);
 
     if (window.fullScreen)
       return;
 
-    // In some edgecases it is possible for this to fire before we've initialized.
-    if (!this._initialized) {
+    // We want to do this from initialization anyway, so that the
+    // "chromemargin" attributes are all correctly setup, but we don't want to
+    // do this before the DOM loads again, to prevent spurious reflows that
+    // will be superseded by the one on onDOMContentLoaded.
+    if (!this._domLoaded && !aFromInit) {
       return;
     }
 
     if (!aForce) {
       // _update is called on resize events, because the window is not ready
       // after sizemode events. However, we only care about the event when the
       // sizemode is different from the last time we updated the appearance of
       // the tabs in the titlebar.
@@ -264,17 +270,16 @@ var TabsInTitlebar = {
   },
 
   _sizePlaceholder(type, width) {
     Array.forEach(document.querySelectorAll(".titlebar-placeholder[type='" + type + "']"),
                   function(node) { node.style.width = width + "px"; });
   },
 
   uninit() {
-    this._initialized = false;
     removeEventListener("resolutionchange", this);
     Services.prefs.removeObserver(this._prefName, this);
     this._menuObserver.disconnect();
     CustomizableUI.removeListener(this);
   }
 };
 
 function updateTitlebarDisplay() {

--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -1292,16 +1292,18 @@ var gBrowserInit = {
       if (uriToLoad == "about:home") {
         gBrowser.setIcon(gBrowser.selectedTab, "chrome://branding/content/icon32.png");
       } else if (uriToLoad == "about:privatebrowsing") {
         gBrowser.setIcon(gBrowser.selectedTab, "chrome://browser/skin/privatebrowsing/favicon.svg");
       }
     });
 
     this._setInitialFocus();
+    gBrowser.tabContainer.updateVisibility();
+    TabsInTitlebar.onDOMContentLoaded();
   },
 
   onLoad() {
     gBrowser.addEventListener("DOMUpdateBlockedPopups", gPopupBlockerObserver);
 
     Services.obs.addObserver(gPluginHandler.NPAPIPluginCrashed, "plugin-crashed");
 
     window.addEventListener("AppCommand", HandleAppCommandEvent, true);

--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -119,17 +119,16 @@
               "emptyPrivateTabTitle" : "emptyTabTitle";
           this.emptyTabTitle = gTabBrowserBundle.GetStringFromName("tabs." + strId);
 
           var tab = this.firstChild;
           tab.label = this.emptyTabTitle;
           tab.setAttribute("onerror", "this.removeAttribute('image');");
 
           window.addEventListener("resize", this);
-          window.addEventListener("DOMContentLoaded", this);
 
           Services.prefs.addObserver("privacy.userContext", this);
           this.observe(null, "nsPref:changed", "privacy.userContext.enabled");
 
           XPCOMUtils.defineLazyPreferenceGetter(this, "_tabMinWidthPref",
             "browser.tabs.tabMinWidth", null,
             (pref, prevValue, newValue) => this._tabMinWidth = newValue,
             newValue => {
@@ -749,19 +748,16 @@
           this._handleTabSelect();
         ]]></body>
       </method>
 
       <method name="handleEvent">
         <parameter name="aEvent"/>
         <body><![CDATA[
           switch (aEvent.type) {
-            case "DOMContentLoaded":
-              this.updateVisibility();
-              break;
             case "resize":
               if (aEvent.target != window)
                 break;
 
               TabsInTitlebar.updateAppearance();
               this._updateCloseButtons();
               this._handleTabSelect(true);
               this.updateSessionRestoreVisibility();