Make Event RefCountedGarbageCollected and implement trace() methods to the Event hierarcy

Source/core/events/ResourceProgressEvent.cpp

Index: Source/core/events/ResourceProgressEvent.cpp
diff --git a/Source/core/events/ResourceProgressEvent.cpp b/Source/core/events/ResourceProgressEvent.cpp
index 59d10d4d27d3b90ca3c3e388afd8c1edfda0fbec..08fd75b2533f636a932341f8d46e0e637511352b 100644
--- a/Source/core/events/ResourceProgressEvent.cpp
+++ b/Source/core/events/ResourceProgressEvent.cpp
@@ -51,4 +51,9 @@ const AtomicString& ResourceProgressEvent::interfaceName() const
     return EventNames::ResourceProgressEvent;
 }
 
+void ResourceProgressEvent::trace(Visitor* visitor)
+{
+    ProgressEvent::trace(visitor);
+}
+
 }