import changes from tenfourfox:

- #443: M1395138 M1400554 M1400003 M1407751 M1261175 (99d4c13d8)
- #443: update certs and pins (ee75e42df)
- #443: M1408412 M1306626 M1404636 M1406398 (622263e71)
- #443: update certs and pins, M1397811 M1407740 M1408005 M1411458 M1406750 M1412252 M1400763 (f79d49e99)

docshell/base/nsDocShell.cpp

@@ -845,6 +845,9 @@ nsDocShell::~nsDocShell()
 {
   MOZ_ASSERT(!mObserved);
 
+  // Avoid notifying observers while we're in the dtor.
+  mIsBeingDestroyed = true;
+
   Destroy();
 
   nsCOMPtr<nsISHistoryInternal> shPrivate(do_QueryInterface(mSessionHistory));