Bug 1662103 - Make .close() a no-op on OOP iframes. r=farre

Differential Revision: https://phabricator.services.mozilla.com/D88983

docshell/base/BrowsingContext.cpp

@@ -1835,6 +1835,11 @@ void BrowsingContext::Close(CallerType aCallerType, ErrorResult& aError) {
     return;
   }
 
+  if (IsFrame()) {
+    // .close() on frames is a no-op.
+    return;
+  }
+
   if (GetDOMWindow()) {
     nsGlobalWindowOuter::Cast(GetDOMWindow())
         ->CloseOuter(aCallerType == CallerType::System);