[Background Sync] Align exposed API with spec

third_party/WebKit/Source/modules/background_sync/SyncEvent.cpp

Index: third_party/WebKit/Source/modules/background_sync/SyncEvent.cpp
diff --git a/third_party/WebKit/Source/modules/background_sync/SyncEvent.cpp b/third_party/WebKit/Source/modules/background_sync/SyncEvent.cpp
index b109a1115e2b6f80c14d51336381a507225570a0..c4f79062e2fab0ecdd751d4bac25eed2cf586779 100644
--- a/third_party/WebKit/Source/modules/background_sync/SyncEvent.cpp
+++ b/third_party/WebKit/Source/modules/background_sync/SyncEvent.cpp
@@ -11,9 +11,9 @@ SyncEvent::SyncEvent()
 {
 }
 
-SyncEvent::SyncEvent(const AtomicString& type, SyncRegistration* syncRegistration, bool lastChance, WaitUntilObserver* observer)
+SyncEvent::SyncEvent(const AtomicString& type, const String& tag, bool lastChance, WaitUntilObserver* observer)
     : ExtendableEvent(type, ExtendableEventInit(), observer)
-    , m_syncRegistration(syncRegistration)
+    , m_tag(tag)
     , m_lastChance(lastChance)
 {
 }
@@ -21,7 +21,7 @@ SyncEvent::SyncEvent(const AtomicString& type, SyncRegistration* syncRegistratio
 SyncEvent::SyncEvent(const AtomicString& type, const SyncEventInit& init)
     : ExtendableEvent(type, init)
 {
-    m_syncRegistration = init.registration();
+    m_tag = init.tag();
     m_lastChance = init.lastChance();
 }
 
@@ -34,9 +34,9 @@ const AtomicString& SyncEvent::interfaceName() const
     return EventNames::SyncEvent;
 }
 
-SyncRegistration* SyncEvent::registration()
+String SyncEvent::tag()
 {
-    return m_syncRegistration.get();
+    return m_tag;
 }
 
 bool SyncEvent::lastChance()
@@ -46,7 +46,6 @@ bool SyncEvent::lastChance()
 
 DEFINE_TRACE(SyncEvent)
 {
-    visitor->trace(m_syncRegistration);
     ExtendableEvent::trace(visitor);
 }