Handle some failing DocumentOrderedMap ID lookups across tree removals.

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

Index: third_party/WebKit/Source/core/dom/TreeScope.cpp
diff --git a/third_party/WebKit/Source/core/dom/TreeScope.cpp b/third_party/WebKit/Source/core/dom/TreeScope.cpp
index d536fa338bfc7b3b18026ab5bd713a888c7d33e8..d4547edd6800d8e5488e98c008a1782540e2dee1 100644
--- a/third_party/WebKit/Source/core/dom/TreeScope.cpp
+++ b/third_party/WebKit/Source/core/dom/TreeScope.cpp
@@ -186,43 +186,11 @@ void TreeScope::addElementById(const AtomicString& elementId, Element* element)
 }
 
 
-#if ENABLE(ASSERT)
-namespace {
-
-class RemovingElementIdScope {
-    STACK_ALLOCATED();
-public:
-    RemovingElementIdScope(DocumentOrderedMap& elementsById, const AtomicString& id)
-        : m_elementsById(&elementsById)
-    {
-        m_elementsById->willRemoveId(id);
-    }
-    ~RemovingElementIdScope()
-    {
-        m_elementsById->willRemoveId(nullAtom);
-    }
-
-private:
-    RawPtrWillBeMember<DocumentOrderedMap> m_elementsById;
-};
-
-}
-#endif
-
 void TreeScope::removeElementById(const AtomicString& elementId, Element* element)
 {
     if (!m_elementsById)
         return;
     m_elementsById->remove(elementId, element);
-#if ENABLE(ASSERT)
-    // Register 'elementId' as being removed. This is done should observers
-    // attempt to also look it up, something that the underlying DocumentOrderedMap
-    // is incapable of answering precisely while an element (and its
-    // children) are being removed from the tree. This is _only_ done to avoid
-    // an assert in DocumentOrderedMap::get() from falsely triggering for such
-    // unusual and unexpected lookups.
-    RemovingElementIdScope removalScope(*m_elementsById, elementId);
-#endif
     m_idTargetObserverRegistry->notifyObservers(elementId);
 }
 
@@ -612,4 +580,24 @@ DEFINE_TRACE(TreeScope)
     visitor->trace(m_scopedStyleResolver);
 }
 
+#if ENABLE(ASSERT)
+TreeScope::RemoveScope::RemoveScope(ContainerNode* containerNode)
+    : m_idMap(containerNode->treeScope().m_elementsById.get())
+{
+    // While removing a ContainerNode, lookups in the underlying id map will

[esprehn, 2016/01/05 07:48:33]

this comment should be with the RemoveScope class in the DocumentOrderedMap
header

[sof, 2016/01/05 12:37:18]

Done, moved to DocumentOrderedMap::RemoveScope declaration.

+    // not be precise should the tree have elements with duplicate IDs
+    // contained in the node being removed. Rare trees, but ID lookups may legitimately
+    // fail across such removals; inform the DocumentOrderedMap about the transitory
+    // state of the underlying tree.
+    if (m_idMap)
+        m_idMap->enterTreeRemoveScope();
+}
+
+TreeScope::RemoveScope::~RemoveScope()
+{
+    if (m_idMap)
+        m_idMap->leaveTreeRemoveScope();
+}
+#endif
+
 } // namespace blink