Bug 1269462 - fix race condition in TabsInTitlebar code where it was possible...

Bug 1269462 - fix race condition in TabsInTitlebar code where it was possible we'd only be called before init(), resulting in never updating the titlebar maths, r=MattN,mconley

MozReview-Commit-ID: KM274gGpiuR

--HG--
extra : rebase_source : 06cfc19ce026cfc033fff0a6b0c6a455c78e0cdf

browser/base/content/browser-tabsintitlebar.js

@@ -38,6 +38,12 @@ var TabsInTitlebar = {
     addEventListener("resolutionchange", this, false);
 
     this._initialized = true;
+    if (this._updateOnInit) {
+      // We don't need to call this with 'true', even if original calls
+      // (before init()) did, because this will be the first call and so
+      // we will update anyway.
+      this._update();
+    }
   },
 
   allowedBy: function (condition, allow) {
@@ -84,6 +90,7 @@ var TabsInTitlebar = {
   },
 
   _initialized: false,
+  _updateOnInit: false,
   _disallowed: {},
   _prefName: "browser.tabs.drawInTitlebar",
   _lastSizeMode: null,
@@ -98,8 +105,15 @@ var TabsInTitlebar = {
     let rect = ele => ele.getBoundingClientRect();
     let verticalMargins = cstyle => parseFloat(cstyle.marginBottom) + parseFloat(cstyle.marginTop);
 
-    if (!this._initialized || window.fullScreen)
+    if (window.fullScreen)
+      return;
+
+    // In some edgecases it is possible for this to fire before we've initialized.
+    // Don't run now, but don't forget to run it when we do initialize.
+    if (!this._initialized) {
+      this._updateOnInit = true;
       return;
+    }
 
     let allowed = true;