Bug 776773 - put tabs in the title bar before updating the tab strip. r=ttaubert

browser/base/content/browser.js

@@ -4681,15 +4681,9 @@ var TabsInTitlebar = {
     this._readPref();
     Services.prefs.addObserver(this._prefName, this, false);
 
-    // Don't trust the initial value of the sizemode attribute; wait for the resize event.
+    // Don't trust the initial value of the sizemode attribute; wait for
+    // the resize event (handled in tabbrowser.xml).
     this.allowedBy("sizemode", false);
-    window.addEventListener("resize", function (event) {
-      if (event.target != window)
-        return;
-      let sizemode = document.documentElement.getAttribute("sizemode");
-      TabsInTitlebar.allowedBy("sizemode",
-                               sizemode == "maximized" || sizemode == "fullscreen");
-    }, false);
 
     this._initialized = true;
 #endif

browser/base/content/tabbrowser.xml

@@ -3092,6 +3092,11 @@
             case "resize":
               if (aEvent.target != window)
                 break;
+
+              let sizemode = document.documentElement.getAttribute("sizemode");
+              TabsInTitlebar.allowedBy("sizemode",
+                                       sizemode == "maximized" || sizemode == "fullscreen");
+
               var width = this.mTabstrip.boxObject.width;
               if (width != this.mTabstripWidth) {
                 this.adjustTabstrip();
@@ -3099,6 +3104,7 @@
                 this._handleTabSelect();
                 this.mTabstripWidth = width;
               }
+
               this.tabbrowser.updateWindowResizers();
               break;
             case "mouseout":