Bug 1663487 - Set loading history entry for loads in the parent. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D89420

docshell/base/nsDocShell.cpp

@@ -13001,5 +13001,7 @@ bool nsDocShell::GetIsAttemptingToNavigate() {
 
 void nsDocShell::SetLoadingSessionHistoryInfo(
     const mozilla::dom::LoadingSessionHistoryInfo& aLoadingInfo) {
+  // FIXME Would like to assert this, but can't yet.
+  // MOZ_ASSERT(!mLoadingEntry);
   mLoadingEntry = MakeUnique<LoadingSessionHistoryInfo>(aLoadingInfo);
 }