Bug 1390273 - Initialize the Sync UI in popup windows. r=Gijs

MozReview-Commit-ID: IDhhXgIrwrB

--HG--
extra : rebase_source : 73e4f9c07aae5239bec1b2e8638baae065bef292

browser/base/content/browser-sync.js

@@ -90,8 +90,7 @@ var gSync = {
   },
 
   init() {
-    // Bail out if we're already initialized or for pop-up windows.
-    if (this._initialized || !window.toolbar.visible) {
+    if (this._initialized) {
       return;
     }