Migrate WTF::HashMap::add() to ::insert()

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

Index: third_party/WebKit/Source/core/dom/SpaceSplitString.cpp
diff --git a/third_party/WebKit/Source/core/dom/SpaceSplitString.cpp b/third_party/WebKit/Source/core/dom/SpaceSplitString.cpp
index 6bf70dd6dcc121ddd1d6f9e1a6acd086a723eff0..86ed50e4421ce1c7e92c4779500f2b88cee652e0 100644
--- a/third_party/WebKit/Source/core/dom/SpaceSplitString.cpp
+++ b/third_party/WebKit/Source/core/dom/SpaceSplitString.cpp
@@ -167,7 +167,7 @@ SpaceSplitString::Data::~Data() {
 
 PassRefPtr<SpaceSplitString::Data> SpaceSplitString::Data::create(
     const AtomicString& string) {
-  Data*& data = sharedDataMap().add(string, nullptr).storedValue->value;
+  Data*& data = sharedDataMap().insert(string, nullptr).storedValue->value;
   if (!data) {
     data = new Data(string);
     return adoptRef(data);