Make HTMLSlotElement.distributedNodeNextTo&distributedNodePreviousTo faster

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

 /*
  * 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 65 matching lines @@
     return m_distributedNodes;
 }
 
 void HTMLSlotElement::appendAssignedNode(Node& node)
 {
     m_assignedNodes.append(&node);
 }
 
 void HTMLSlotElement::appendDistributedNode(Node& node)
 {
+    size_t size = m_distributedNodes.size();
     m_distributedNodes.append(&node);
+    m_distributedIndices.set(&node, size);
 }
 
 void HTMLSlotElement::appendDistributedNodesFrom(const HTMLSlotElement& other)
 {
+    size_t index = m_distributedNodes.size();
     m_distributedNodes.appendVector(other.m_distributedNodes);
+    for (const auto& it : other.m_distributedIndices) {
+        const Node* node = it.key;
+        m_distributedIndices.set(node, index++);
+    }
 }
 
 void HTMLSlotElement::clearDistribution()
 {
     m_assignedNodes.clear();
     m_distributedNodes.clear();
+    m_distributedIndices.clear();
 }
 
 Node* HTMLSlotElement::distributedNodeNextTo(const Node& node) const
 {
-    size_t index = m_distributedNodes.find(&node);
-    if (index == kNotFound || index + 1 == m_distributedNodes.size())
+    const auto& it = m_distributedIndices.find(&node);

[kochi, 2016/02/01 06:12:15]

Yeah, 'const auto&' is better than 'const auto'.

+    if (it == m_distributedIndices.end())
+        return nullptr;
+    size_t index = it->value;
+    if (index + 1 == m_distributedNodes.size())
         return nullptr;
     return m_distributedNodes[index + 1].get();
 }
 
 Node* HTMLSlotElement::distributedNodePreviousTo(const Node& node) const
 {
-    size_t index = m_distributedNodes.find(&node);
-    if (index == kNotFound || index == 0)
+    const auto& it = m_distributedIndices.find(&node);
+    if (it == m_distributedIndices.end())
+        return nullptr;
+    size_t index = it->value;
+    if (index == 0)
         return nullptr;
     return m_distributedNodes[index - 1].get();
 }
 
 void HTMLSlotElement::attach(const AttachContext& context)
 {
     for (auto& node : m_distributedNodes) {
         if (node->needsAttach())
             node->attach(context);
     }
@@ skipping 73 matching lines @@
             continue;
         if (isHTMLSlotElement(child))
             appendDistributedNodesFrom(toHTMLSlotElement(child));
         else
             appendDistributedNode(child);
     }
 }
 
 DEFINE_TRACE(HTMLSlotElement)
 {
+#if ENABLE(OILPAN)
     visitor->trace(m_assignedNodes);
     visitor->trace(m_distributedNodes);
+    visitor->trace(m_distributedIndices);
+#endif
     HTMLElement::trace(visitor);
 }
 
 } // namespace blink