Oilpan: move custom element objects to the heap.

Source/core/dom/custom/CustomElementMicrotaskStep.h

Index: Source/core/dom/custom/CustomElementMicrotaskStep.h
diff --git a/Source/core/dom/custom/CustomElementMicrotaskStep.h b/Source/core/dom/custom/CustomElementMicrotaskStep.h
index d4678cda25803f9a863f253b25bf30907281ffbf..80fd9724a98cc702c967d3f8a6539f9e136d7d70 100644
--- a/Source/core/dom/custom/CustomElementMicrotaskStep.h
+++ b/Source/core/dom/custom/CustomElementMicrotaskStep.h
@@ -31,11 +31,12 @@
 #ifndef CustomElementMicrotaskStep_h
 #define CustomElementMicrotaskStep_h
 
+#include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 
 namespace WebCore {
 
-class CustomElementMicrotaskStep {
+class CustomElementMicrotaskStep : public NoBaseWillBeGarbageCollectedFinalized<CustomElementMicrotaskStep> {
     WTF_MAKE_NONCOPYABLE(CustomElementMicrotaskStep);
 public:
     CustomElementMicrotaskStep() { }
@@ -50,6 +51,8 @@ public:
     virtual Result process() = 0;
     virtual bool needsProcessOrStop() const = 0;
 
+    virtual void trace(Visitor*) { }
+
 #if !defined(NDEBUG)
     virtual void show(unsigned indent) = 0;
 #endif