Simpler return value from HashTable::add()/HashMap::add() and others

Source/core/dom/custom/CustomElementUpgradeCandidateMap.cpp

Index: Source/core/dom/custom/CustomElementUpgradeCandidateMap.cpp
diff --git a/Source/core/dom/custom/CustomElementUpgradeCandidateMap.cpp b/Source/core/dom/custom/CustomElementUpgradeCandidateMap.cpp
index b7ea628bd484b67024d0328d08ade36df57c6398..ccbbed39b8fba00d16423aee900933929ea26b33 100644
--- a/Source/core/dom/custom/CustomElementUpgradeCandidateMap.cpp
+++ b/Source/core/dom/custom/CustomElementUpgradeCandidateMap.cpp
@@ -50,9 +50,12 @@ void CustomElementUpgradeCandidateMap::add(const CustomElementDescriptor& descri
     ASSERT_UNUSED(result, result.isNewEntry);
 
     UnresolvedDefinitionMap::iterator it = m_unresolvedDefinitions.find(descriptor);
+    ElementSet* elements;
     if (it == m_unresolvedDefinitions.end())
-        it = m_unresolvedDefinitions.add(descriptor, ElementSet()).iterator;
-    it->value.add(element);
+        elements = &m_unresolvedDefinitions.add(descriptor, ElementSet()).storedValue->value;
+    else
+        elements = &it->value;
+    elements->add(element);
 }
 
 void CustomElementUpgradeCandidateMap::remove(Element* element)