Add [WillBeGarbageCollected] to Event.idl

Source/bindings/templates/interface.cpp

Index: Source/bindings/templates/interface.cpp
diff --git a/Source/bindings/templates/interface.cpp b/Source/bindings/templates/interface.cpp
index 28204a139f4403aa4507e45f44644a8baa5e5da2..01f4a6c16627d12e4017dbb6a3a490874ba00c3e 100644
--- a/Source/bindings/templates/interface.cpp
+++ b/Source/bindings/templates/interface.cpp
@@ -647,7 +647,7 @@ static void constructor(const v8::FunctionCallbackInfo<v8::Value>& info)
     if (exceptionState.throwIfNeeded())
         return;
     {% else %}
-    RefPtr<{{cpp_class}}> event = {{cpp_class}}::create(type, eventInit);
+    RefPtrWillBeRawPtr<{{cpp_class}}> event = {{cpp_class}}::create(type, eventInit);
     {% endif %}
     {% if any_type_attributes and not interface_name == 'ErrorEvent' %}
     {# If we're in an isolated world, create a SerializedScriptValue and store