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

third_party/WebKit/Source/platform/LifecycleNotifier.h

Index: third_party/WebKit/Source/platform/LifecycleNotifier.h
diff --git a/third_party/WebKit/Source/platform/LifecycleNotifier.h b/third_party/WebKit/Source/platform/LifecycleNotifier.h
index f6b7412d2ac4620161c213929df8a7566b98f2c7..cf1480ee1a294e753ca65effe357bec04b9fa6f0 100644
--- a/third_party/WebKit/Source/platform/LifecycleNotifier.h
+++ b/third_party/WebKit/Source/platform/LifecycleNotifier.h
@@ -145,7 +145,7 @@ inline void LifecycleNotifier<T, Observer>::notifyContextDestroyed() {
 template <typename T, typename Observer>
 inline void LifecycleNotifier<T, Observer>::addObserver(Observer* observer) {
   RELEASE_ASSERT(m_iterationState & AllowingAddition);
-  m_observers.add(observer);
+  m_observers.insert(observer);
 }
 
 template <typename T, typename Observer>
@@ -153,7 +153,7 @@ inline void LifecycleNotifier<T, Observer>::removeObserver(Observer* observer) {
   // If immediate removal isn't currently allowed,
   // |observer| is recorded for pending removal.
   if (m_iterationState & AllowPendingRemoval) {
-    m_observers.add(observer);
+    m_observers.insert(observer);
     return;
   }
   RELEASE_ASSERT(m_iterationState & AllowingRemoval);