Add a pre-finalizer to PromiseRejectionEvent

third_party/WebKit/Source/core/events/PromiseRejectionEvent.cpp

Index: third_party/WebKit/Source/core/events/PromiseRejectionEvent.cpp
diff --git a/third_party/WebKit/Source/core/events/PromiseRejectionEvent.cpp b/third_party/WebKit/Source/core/events/PromiseRejectionEvent.cpp
index ec621fc9becbad9dd145606d5057124abdccc440..06d029598a2779cb06b87609d5fd300f8e45004a 100644
--- a/third_party/WebKit/Source/core/events/PromiseRejectionEvent.cpp
+++ b/third_party/WebKit/Source/core/events/PromiseRejectionEvent.cpp
@@ -17,6 +17,7 @@ PromiseRejectionEvent::PromiseRejectionEvent(ScriptState* state, const AtomicStr
     : Event(type, initializer)
     , m_scriptState(state)
 {
+    ThreadState::current()->registerPreFinalizer(this);
     ASSERT(initializer.hasPromise());
     m_promise.set(initializer.promise().isolate(), initializer.promise().v8Value());
     m_promise.setPhantom();
@@ -30,6 +31,15 @@ PromiseRejectionEvent::~PromiseRejectionEvent()
 {
 }
 
+void PromiseRejectionEvent::dispose()
+{
+    // Clear ScopedPersistents so that V8 doesn't call phantom callbacks
+    // (and touch the ScopedPersistents) after Oilpan starts lazy sweeping.
+    m_promise.clear();
+    m_reason.clear();
+    m_scriptState.clear();
+}
+
 ScriptPromise PromiseRejectionEvent::promise(ScriptState* state) const
 {
     // Return null when the promise is accessed by a different world than the world that created the promise.