From 330e68161e08b832824dd33c5f87cb92ef963786 Mon Sep 17 00:00:00 2001
From: Ehsan Akhgari <ehsan@mozilla.com>
Date: Wed, 19 Dec 2018 14:15:57 +0000
Subject: [PATCH] Bug 1514762 - Delay modifying the observer list until we hit
 the event loop; r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D14830
---
 dom/base/nsGlobalWindowOuter.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index 0a5aa7e3cbc8e..f972d4830ca01 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -7265,7 +7265,12 @@ mozilla::dom::TabGroup* nsPIDOMWindowOuter::TabGroup() {
   window->InitWasOffline();
   nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
   if (obs) {
-    obs->AddObserver(window, PERM_CHANGE_NOTIFICATION, true);
+    // Delay calling AddObserver until we hit the event loop, in case we may be
+    // in the middle of modifying the observer list somehow.
+    NS_DispatchToMainThread(
+        NS_NewRunnableFunction("PermChangeDelayRunnable", [obs, window] {
+          obs->AddObserver(window, PERM_CHANGE_NOTIFICATION, true);
+        }));
   }
   nsCOMPtr<nsIPrefBranch> prefBranch = do_GetService(NS_PREFSERVICE_CONTRACTID);
   if (prefBranch) {