Migrate WTF::HashSet::add() to ::insert() [part 1 of N]

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

Index: third_party/WebKit/Source/core/html/HTMLCollection.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCollection.cpp b/third_party/WebKit/Source/core/html/HTMLCollection.cpp
index 33a3c2fd9f7e572191672575532e4a1f412276a5..05d54114d36d9ea4453ea1a00c900ead312c77a3 100644
--- a/third_party/WebKit/Source/core/html/HTMLCollection.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCollection.cpp
@@ -455,7 +455,7 @@ void HTMLCollection::supportedPropertyNames(Vector<String>& names) {
     const AtomicString& idAttribute = element->getIdAttribute();
     if (!idAttribute.isEmpty()) {
       HashSet<AtomicString>::AddResult addResult =
-          existingNames.add(idAttribute);
+          existingNames.insert(idAttribute);
       if (addResult.isNewEntry)
         names.push_back(idAttribute);
     }
@@ -466,7 +466,7 @@ void HTMLCollection::supportedPropertyNames(Vector<String>& names) {
         (type() != DocAll ||
          nameShouldBeVisibleInDocumentAll(toHTMLElement(*element)))) {
       HashSet<AtomicString>::AddResult addResult =
-          existingNames.add(nameAttribute);
+          existingNames.insert(nameAttribute);
       if (addResult.isNewEntry)
         names.push_back(nameAttribute);
     }