Custom Elements: Encapsulates Async and Sync Queues into one class.

Source/core/dom/custom/CustomElementMicrotaskQueueBase.cpp

+// Copyright 2014 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.
+
+#include "config.h"
+#include "core/dom/custom/CustomElementMicrotaskQueueBase.h"
+
+#include "core/dom/custom/CustomElementCallbackDispatcher.h"
+
+namespace WebCore {
+
+class MicrotaskQueueInvocationScope {
+public:
+#if defined(NDEBUG)
+    explicit MicrotaskQueueInvocationScope(CustomElementMicrotaskQueueBase*) { }
+#else
+    explicit MicrotaskQueueInvocationScope(CustomElementMicrotaskQueueBase* queue)
+        : m_parent(s_top)
+        , m_queue(queue)
+    {
+        s_top = this;
+        ASSERT(m_queue->isEmpty() || !hasReenter());

[dominicc (has gone to gerrit), 2014/06/18 00:11:28]

Depending on doDispatch, is it worth making this
ASSERT_WITH_SECURITY_IMPLICATION and always doing this check?

[Hajime Morrita, 2014/06/18 00:57:05]

Done.

+    }
+
+    ~MicrotaskQueueInvocationScope()
+    {
+        s_top = m_parent;
+    }
+
+private:
+    bool hasReenter() const

[dominicc (has gone to gerrit), 2014/06/18 00:11:28]

This looks like a move, but consider renaming this hasReentered?

[Hajime Morrita, 2014/06/18 00:57:05]

Done.

+    {
+        for (MicrotaskQueueInvocationScope* scope = this->m_parent; scope; scope = scope->m_parent) {
+            if (scope->m_queue == m_queue)
+                return true;
+        }
+
+        return false;
+    }
+
+    MicrotaskQueueInvocationScope* m_parent;
+    CustomElementMicrotaskQueueBase* m_queue;
+
+    static MicrotaskQueueInvocationScope* s_top;
+#endif
+};
+
+#if !defined(NDEBUG)
+MicrotaskQueueInvocationScope* MicrotaskQueueInvocationScope::s_top = 0;
+#endif
+
+void CustomElementMicrotaskQueueBase::dispatch()
+{
+    MicrotaskQueueInvocationScope scope(this);

[dominicc (has gone to gerrit), 2014/06/18 00:11:28]

Why do all of this when a simple bool m_inDispatch will give you the same
assertion in four lines of code instead of ~25?

[Hajime Morrita, 2014/06/18 00:57:05]

Done.

+    doDispatch();
+}
+
+void CustomElementMicrotaskQueueBase::trace(Visitor* visitor)
+{
+    visitor->trace(m_queue);
+}
+
+#if !defined(NDEBUG)
+void CustomElementMicrotaskQueueBase::show(unsigned indent)
+{
+    for (unsigned q = 0; q < m_queue.size(); ++q) {
+        if (m_queue[q])
+            m_queue[q]->show(indent);
+        else
+            fprintf(stderr, "%*snull\n", indent, "");
+    }
+}
+#endif
+
+} // namespace WebCore