Merge the Sky Engine changes from the SkyDart branch

sky/engine/core/events/EventTarget.h

Index: sky/engine/core/events/EventTarget.h
diff --git a/sky/engine/core/events/EventTarget.h b/sky/engine/core/events/EventTarget.h
index 9299861cb0b3623d6e0d9373fbb85909312d9733..79134b5ecb123d92b42030478546801bb7adbb51 100644
--- a/sky/engine/core/events/EventTarget.h
+++ b/sky/engine/core/events/EventTarget.h
@@ -37,7 +37,7 @@
 #include "gen/sky/core/EventTargetInterfaces.h"
 #include "gen/sky/core/EventTargetNames.h"
 #include "gen/sky/core/EventTypeNames.h"
-#include "sky/engine/bindings/core/v8/ScriptWrappable.h"
+#include "sky/engine/tonic/dart_wrappable.h"
 #include "sky/engine/core/events/EventListenerMap.h"
 #include "sky/engine/platform/heap/Handle.h"
 #include "sky/engine/wtf/text/AtomicString.h"
@@ -89,7 +89,7 @@ public:
 //
 // Optionally, add a FooEvent.idl class, but that's outside the scope of this
 // comment (and much more straightforward).
-class EventTarget : public ScriptWrappable {
+class EventTarget : public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
 #if !ENABLE(OILPAN)
@@ -97,6 +97,8 @@ public:
     void deref() { derefEventTarget(); }
 #endif
 
+    void AcceptDartGCVisitor(DartGCVisitor& visitor) const override;
+
     virtual const AtomicString& interfaceName() const = 0;
     virtual ExecutionContext* executionContext() const = 0;