Add NotificationEvent.action property in SW events

Source/modules/notifications/NotificationEvent.cpp

Index: Source/modules/notifications/NotificationEvent.cpp
diff --git a/Source/modules/notifications/NotificationEvent.cpp b/Source/modules/notifications/NotificationEvent.cpp
index 9d30dceb30ad879e610ebf496b3ff7c981f0217a..d04fcb393825d4b6f4660885a3c530f0ad671fe4 100644
--- a/Source/modules/notifications/NotificationEvent.cpp
+++ b/Source/modules/notifications/NotificationEvent.cpp
@@ -4,15 +4,18 @@
 
 #include "config.h"
 #include "modules/notifications/NotificationEvent.h"
+#include "wtf/text/WTFString.h"
 
 namespace blink {
 
 NotificationEvent::NotificationEvent()
+    : m_action(emptyString())
 {
 }
 
 NotificationEvent::NotificationEvent(const AtomicString& type, const NotificationEventInit& initializer)
     : ExtendableEvent(type, initializer)
+    , m_action(initializer.action())
 {
     if (initializer.hasNotification())
         m_notification = initializer.notification();
@@ -20,6 +23,7 @@ NotificationEvent::NotificationEvent(const AtomicString& type, const Notificatio
 
 NotificationEvent::NotificationEvent(const AtomicString& type, const NotificationEventInit& initializer, WaitUntilObserver* observer)
     : ExtendableEvent(type, initializer, observer)
+    , m_action(initializer.action())
 {
     if (initializer.hasNotification())
         m_notification = initializer.notification();