Rewrite Shadow DOM distribution engine to support partial synchronous distribution for v1

third_party/WebKit/Source/core/html/HTMLSlotElement.h

 /*
  * Copyright (C) 2015 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 25 matching lines @@
 
 namespace blink {
 
 class AssignedNodesOptions;
 
 class CORE_EXPORT HTMLSlotElement final : public HTMLElement {
     DEFINE_WRAPPERTYPEINFO();
 public:
     DECLARE_NODE_FACTORY(HTMLSlotElement);
 
-    const HeapVector<Member<Node>>& assignedNodes() const { return m_assignedNodes; }
+    const HeapVector<Member<Node>>& assignedNodes();
     const HeapVector<Member<Node>>& getDistributedNodes();
     const HeapVector<Member<Node>> assignedNodesForBinding(const AssignedNodesOptions&);
 
     Node* firstDistributedNode() const { return m_distributedNodes.isEmpty() ? nullptr : m_distributedNodes.first().get(); }
     Node* lastDistributedNode() const { return m_distributedNodes.isEmpty() ? nullptr : m_distributedNodes.last().get(); }
 
     Node* distributedNodeNextTo(const Node&) const;
     Node* distributedNodePreviousTo(const Node&) const;
 
     void appendAssignedNode(Node&);
-    void willUpdateAssignment();
+
+    void resolveDistributedNodes();
     void appendDistributedNode(Node&);
     void appendDistributedNodesFrom(const HTMLSlotElement& other);
-    void willUpdateDistribution();
-    void appendFallbackNode(Node&);
-    void willUpdateFallback();
 
-    void didUpdateAssignment();
-    void updateFallbackNodes();
     void updateDistributedNodesWithFallback();
-    void didUpdateDistribution();
-
-    void fireSlotChangeEvent();
 
     void attach(const AttachContext& = AttachContext()) final;
     void detach(const AttachContext& = AttachContext()) final;
 
     void attributeChanged(const QualifiedName&, const AtomicString& oldValue, const AtomicString& newValue, AttributeModificationReason = ModifiedDirectly) final;
 
     short tabIndex() const override;
     AtomicString name() const;
 
+    // This method can be slow because this has to traverse the children of a shadow host.
+    // This method should be used only when m_assignedNodes is dirty.
+    // e.g. To detect a slotchange event in DOM mutations.
+    bool hasAssignedNodesSlow() const;
+    bool findHostChildWithSameSlotName() const;
+
+    void enqueueSlotChangeEvent();
+
+    void clearDistribution();
+
+    static AtomicString normalizeSlotName(const AtomicString&);
+
     DECLARE_VIRTUAL_TRACE();
 
 private:
     HTMLSlotElement(Document&);
 
-    enum AssignmentState {
-        AssignmentOnGoing,
-        AssignmentDone,
-        AssignmentChanged,
-        AssignmentUnchanged
-    };
-
-    enum DistributionState {
-        DistributionOnGoing,
-        DistributionDone,
-        DistributionChanged,
-        DistributionUnchanged
-    };
-
-    void clearDistribution();
-    void childrenChanged(const ChildrenChange&) final;
     InsertionNotificationRequest insertedInto(ContainerNode*) final;
     void removedFrom(ContainerNode*) final;
     void willRecalcStyle(StyleRecalcChange) final;
 
     void dispatchSlotChangeEvent();
-    bool assignmentChanged();
-    bool distributionChanged();
-    bool fallbackChanged();
 
     HeapVector<Member<Node>> m_assignedNodes;
     HeapVector<Member<Node>> m_distributedNodes;
-    HeapVector<Member<Node>> m_fallbackNodes;
     HeapHashMap<Member<const Node>, size_t> m_distributedIndices;
-    HeapVector<Member<Node>> m_oldAssignedNodes;
-    // TODO(hayato): Remove m_oldDistibutedNodes and make SlotAssignment check the diffirence between old and new distributed nodes for each slot to save the memories.
-    HeapVector<Member<Node>> m_oldDistributedNodes;
-    HeapVector<Member<Node>> m_oldFallbackNodes;
-    DistributionState m_distributionState;
-    AssignmentState m_assignmentState;
-    bool m_slotchangeEventAdded;
+    bool m_slotchangeEventEnqueued = false;
 };
 
 } // namespace blink
 
 #endif // HTMLSlotElement_h