Better handling of DocumentOrderedMap same-ID lookups during tree removals

third_party/WebKit/Source/core/dom/DocumentOrderedMap.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple 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 23 matching lines @@
 #include "core/HTMLNames.h"
 #include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/TreeScope.h"
 #include "core/html/HTMLMapElement.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
+
+PassOwnPtrWillBeRawPtr<DocumentOrderedMap> DocumentOrderedMap::create()
+{
+    return adoptPtrWillBeNoop(new DocumentOrderedMap);
+}
+
+DocumentOrderedMap::DocumentOrderedMap()
+{
+}
+
+DocumentOrderedMap::~DocumentOrderedMap()
+{
+}
+
 inline bool keyMatchesId(const AtomicString& key, const Element& element)
 {
     return element.getIdAttribute() == key;
 }
 
 inline bool keyMatchesMapName(const AtomicString& key, const Element& element)
 {
     return isHTMLMapElement(element) && toHTMLMapElement(element).getName() == key;
 }
 
 inline bool keyMatchesLowercasedMapName(const AtomicString& key, const Element& element)
 {
     return isHTMLMapElement(element) && toHTMLMapElement(element).getName().lower() == key;
 }
 
 inline bool keyMatchesLabelForAttribute(const AtomicString& key, const Element& element)
 {
     return isHTMLLabelElement(element) && element.getAttribute(forAttr) == key;
 }
 
-PassOwnPtrWillBeRawPtr<DocumentOrderedMap> DocumentOrderedMap::create()
-{
-    return adoptPtrWillBeNoop(new DocumentOrderedMap());
-}
-
 void DocumentOrderedMap::add(const AtomicString& key, Element* element)
 {
     ASSERT(key);
     ASSERT(element);
 
     Map::AddResult addResult = m_map.add(key, adoptPtrWillBeNoop(new MapEntry(element)));
     if (addResult.isNewEntry)
         return;
 
     OwnPtrWillBeMember<MapEntry>& entry = addResult.storedValue->value;
@@ skipping 20 matching lines @@
     } else {
         if (entry->element == element) {
             ASSERT(entry->orderedList.isEmpty() || entry->orderedList.first() == element);
             entry->element = entry->orderedList.size() > 1 ? entry->orderedList[1] : nullptr;
         }
         entry->count--;
         entry->orderedList.clear();
     }
 }
 
+#if ENABLE(ASSERT)
+void DocumentOrderedMap::willRemoveId(const AtomicString& key)
+{
+    ASSERT(m_removingId.isNull() || key.isNull());
+    m_removingId = key;
+}
+#endif
+
 template<bool keyMatches(const AtomicString&, const Element&)>
 inline Element* DocumentOrderedMap::get(const AtomicString& key, const TreeScope* scope) const
 {
     ASSERT(key);
     ASSERT(scope);
 
     MapEntry* entry = m_map.get(key);
     if (!entry)
         return 0;
 
     ASSERT(entry->count);
     if (entry->element)
         return entry->element;
 
-    // We know there's at least one node that matches; iterate to find the first one.
+    // Iterate to find the node that matches. Nothing will match iff an element
+    // with children having duplicate IDs is being removed -- the tree traversal
+    // will be over an updated tree not having that element. In all other cases,
+    // a match is expected.
+    //
+    // Such calls to get()/getElementById() while handling element removals will
+    // legitimately happen when e.g., adjusting form ID associations. Quietly
+    // allow those lookups to (expectedly) fail by having the tree scope removal
+    // register the element ID it is in the process of removing.
     for (Element& element : ElementTraversal::startsAfter(scope->rootNode())) {
         if (!keyMatches(key, element))
             continue;
         entry->element = &element;
         return &element;
     }
-    ASSERT_NOT_REACHED();
+    ASSERT(key == m_removingId);
     return 0;
 }
 
 Element* DocumentOrderedMap::getElementById(const AtomicString& key, const TreeScope* scope) const
 {
     return get<keyMatchesId>(key, scope);
 }
 
 const WillBeHeapVector<RawPtrWillBeMember<Element>>& DocumentOrderedMap::getAllElementsById(const AtomicString& key, const TreeScope* scope) const
 {
@@ skipping 47 matching lines @@
 
 DEFINE_TRACE(DocumentOrderedMap::MapEntry)
 {
     visitor->trace(element);
 #if ENABLE(OILPAN)
     visitor->trace(orderedList);
 #endif
 }
 
 } // namespace blink