HTML Imports: No more BlockingDocumentCreation.

Source/core/dom/custom/CustomElementMicrotaskQueue.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/dom/custom/CustomElementMicrotaskQueue.h"
 
 #include "core/dom/custom/CustomElementCallbackDispatcher.h"
 
 namespace WebCore {
 
+class MicrotaskQueueInvocationScope {
+public:
+#if defined(NDEBUG)
+    explicit MicrotaskQueueInvocationScope(CustomElementMicrotaskQueue*) { }
+#else
+    explicit MicrotaskQueueInvocationScope(CustomElementMicrotaskQueue* queue)
+        : m_parent(s_top)
+        , m_queue(queue)
+    {
+        s_top = this;
+        ASSERT(m_queue->isEmpty() || !hasReenter());
+    }
+
+    ~MicrotaskQueueInvocationScope()
+    {
+        s_top = m_parent;
+    }
+
+private:
+    bool hasReenter() const
+    {
+        for (MicrotaskQueueInvocationScope* scope = this->m_parent; scope; scope = scope->m_parent) {
+            if (scope->m_queue == m_queue)
+                return true;
+        }
+
+        return false;
+    }
+
+    MicrotaskQueueInvocationScope* m_parent;
+    CustomElementMicrotaskQueue* m_queue;
+
+    static MicrotaskQueueInvocationScope* s_top;
+#endif
+};
+
+#if !defined(NDEBUG)
+MicrotaskQueueInvocationScope* MicrotaskQueueInvocationScope::s_top = 0;
+#endif
+
 void CustomElementMicrotaskQueue::enqueue(PassOwnPtr<CustomElementMicrotaskStep> step)
 {
     m_queue.append(step);
 }
 
 CustomElementMicrotaskStep::Result CustomElementMicrotaskQueue::dispatch()
 {
+    MicrotaskQueueInvocationScope scope(this);
     Result result = Result(0);
 
     unsigned i;
     for (i = 0; i < m_queue.size(); ++i) {
         result = Result(result | m_queue[i]->process());
 
         if (result & CustomElementMicrotaskStep::ShouldStop)
             break;
     }
 
     bool wasStopped = i < m_queue.size();
     if (wasStopped)
         m_queue.remove(0, i);
     else
         m_queue.resize(0);
 
     return result;
 }
 
 } // namespace WebCore