Add a stack of queues of elements with reaction queues.

third_party/WebKit/Source/core/dom/custom/CustomElementReactionStack.cpp

Index: third_party/WebKit/Source/core/dom/custom/CustomElementReactionStack.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementReactionStack.cpp b/third_party/WebKit/Source/core/dom/custom/CustomElementReactionStack.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6d81441dce2701611a473290982a2ae093e51d48
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementReactionStack.cpp
@@ -0,0 +1,67 @@
+// 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.
+
+#include "core/dom/custom/CustomElementReactionStack.h"
+
+#include "core/dom/Element.h"
+#include "core/dom/custom/CustomElementReactionQueue.h"
+
+namespace blink {
+
+// TODO(dominicc): Consider using linked heap structures, avoiding
+// finalizers, to make short-lived entries fast.
+
+CustomElementReactionStack::CustomElementReactionStack()
+{
+}
+
+CustomElementReactionStack::~CustomElementReactionStack()
+{
+}
+
+DEFINE_TRACE(CustomElementReactionStack)
+{
+    visitor->trace(m_map);
+    visitor->trace(m_stack);
+}
+
+void CustomElementReactionStack::push()
+{
+    m_stack.append(nullptr);
+}
+
+void CustomElementReactionStack::popInvokingReactions()
+{
+    ElementQueue* queue = m_stack.last();
+    m_stack.removeLast();
+    if (!queue)
+        return;
+    for (auto& element : *queue) {
+        if (CustomElementReactionQueue* reactions = m_map.get(element)) {
+            reactions->invokeReactions(element);
+            CHECK(reactions->isEmpty());
+            m_map.remove(element);
+        }
+    }
+}
+
+void CustomElementReactionStack::enqueue(
+    Element* element,
+    CustomElementReaction* reaction)
+{
+    ElementQueue* queue = m_stack.last();
+    if (!queue)
+        m_stack.last() = queue = new ElementQueue();
+    queue->append(element);
+
+    CustomElementReactionQueue* reactions = m_map.get(element);
+    if (!reactions) {
+        reactions = new CustomElementReactionQueue();
+        m_map.add(element, reactions);
+    }
+
+    reactions->add(reaction);
+}
+
+} // namespace blink