Bug 1286930 - Allow the About dialog to show the application update UI even if the separate Update Available window is shown. r=rstrong

MozReview-Commit-ID: 1jUyLx4KsZG

--HG--
extra : rebase_source : fe2e29b29fa50e21f3c426f51e2504b9095c4812

browser/base/content/aboutDialog-appUpdater.js

@@ -28,9 +28,12 @@ function appUpdater()
 {
   this.updateDeck = document.getElementById("updateDeck");
 
-  // Hide the update deck when there is already an update window open to avoid
+  // Hide the update deck when the update window is already open and it's not
-  // syncing issues between them.
+  // already applied, to avoid syncing issues between them. Applied updates
-  if (Services.wm.getMostRecentWindow("Update:Wizard")) {
+  // don't have any information to sync between the windows as they both just
+  // show the "Restart to continue"-type button.
+  if (Services.wm.getMostRecentWindow("Update:Wizard") &&
+      !this.isApplied) {
     this.updateDeck.hidden = true;
     return;
   }