The HTML parser synchronously creates custom elements

third_party/WebKit/Source/core/dom/custom/CEReactionsScope.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CEReactionsScope_h
 #define CEReactionsScope_h
 
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Allocator.h"
@@ skipping 23 matching lines @@
     }
 
     ~CEReactionsScope()
     {
         if (m_frameHost.get())
             invokeReactions();
         s_topOfStack = s_topOfStack->m_prev;
     }
 
     void enqueueToCurrentQueue(Element*, CustomElementReaction*);
+    bool isEmpty() { return !m_frameHost; }
 
 private:
     static CEReactionsScope* s_topOfStack;
 
     void invokeReactions();
 
     CEReactionsScope* m_prev;
     Member<FrameHost> m_frameHost;
 };
 
 } // namespace blink
 
 #endif // CEReactionsScope_h