Bug 1273094 - only trigger TabsInTitlebar.init() after the tabbrowser has updated the visibility of the tabs toolbar, r=mikedeboer

MozReview-Commit-ID: 2NOPYqbq4Zp

--HG--
extra : rebase_source : fcafa79a232d994ad56e73539134a2f01934a210
extra : amend_source : 42aad7336111e104b44c2286932bbbf409db5914

browser/base/content/browser-tabsintitlebar.js

@@ -8,6 +8,9 @@
 
 var TabsInTitlebar = {
   init: function () {
+    if (this._initialized) {
+      return;
+    }
     this._readPref();
     Services.prefs.addObserver(this._prefName, this, false);
 

browser/base/content/browser.js

@@ -990,7 +990,6 @@ var gBrowserInit = {
     TabletModeUpdater.init();
     CombinedStopReload.init();
     gPrivateBrowsingUI.init();
-    TabsInTitlebar.init();
 
     if (window.matchMedia("(-moz-os-version: windows-win8)").matches &&
         window.matchMedia("(-moz-windows-default-theme)").matches) {
@@ -5099,12 +5098,15 @@ var TabletModeUpdater = {
   },
 
   update(isInTabletMode) {
+    let wasInTabletMode = document.documentElement.hasAttribute("tabletmode");
     if (isInTabletMode) {
       document.documentElement.setAttribute("tabletmode", "true");
     } else {
       document.documentElement.removeAttribute("tabletmode");
     }
-    TabsInTitlebar.updateAppearance(true);
+    if (wasInTabletMode != isInTabletMode) {
+      TabsInTitlebar.updateAppearance(true);
+    }
   },
 };
 

browser/base/content/tabbrowser.xml

@@ -5364,6 +5364,7 @@
           switch (aEvent.type) {
             case "load":
               this.updateVisibility();
+              TabsInTitlebar.init();
               break;
             case "resize":
               if (aEvent.target != window)