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

third_party/WebKit/Source/core/animation/StringKeyframe.cpp

Index: third_party/WebKit/Source/core/animation/StringKeyframe.cpp
diff --git a/third_party/WebKit/Source/core/animation/StringKeyframe.cpp b/third_party/WebKit/Source/core/animation/StringKeyframe.cpp
index 7f6bb9ff9a12d9a22745bbcbd3278c741543413d..5a522fe77ac8a0fab0e61f70b5c931cb91ed453f 100644
--- a/third_party/WebKit/Source/core/animation/StringKeyframe.cpp
+++ b/third_party/WebKit/Source/core/animation/StringKeyframe.cpp
@@ -79,18 +79,18 @@ PropertyHandleSet StringKeyframe::properties() const {
         << "Web Animations: Encountered unexpanded shorthand CSS property ("
         << propertyReference.id() << ").";
     if (propertyReference.id() == CSSPropertyVariable)
-      properties.add(PropertyHandle(
+      properties.insert(PropertyHandle(
           toCSSCustomPropertyDeclaration(propertyReference.value()).name()));
     else
-      properties.add(PropertyHandle(propertyReference.id(), false));
+      properties.insert(PropertyHandle(propertyReference.id(), false));
   }
 
   for (unsigned i = 0; i < m_presentationAttributeMap->propertyCount(); ++i)
-    properties.add(
+    properties.insert(
         PropertyHandle(m_presentationAttributeMap->propertyAt(i).id(), true));
 
   for (const auto& key : m_svgAttributeMap.keys())
-    properties.add(PropertyHandle(*key));
+    properties.insert(PropertyHandle(*key));
 
   return properties;
 }