Remove various Heap* types.

sky/engine/core/html/HTMLCanvasElement.h

Index: sky/engine/core/html/HTMLCanvasElement.h
diff --git a/sky/engine/core/html/HTMLCanvasElement.h b/sky/engine/core/html/HTMLCanvasElement.h
index b929635f674d430c83d1fcda24e8a3e2074e05ac..a1cf937e8818cf010d669b030b6d9ea6ffaa2b46 100644
--- a/sky/engine/core/html/HTMLCanvasElement.h
+++ b/sky/engine/core/html/HTMLCanvasElement.h
@@ -65,8 +65,6 @@ public:
 #if !ENABLE(OILPAN)
     virtual void canvasDestroyed(HTMLCanvasElement*) = 0;
 #endif
-
-    virtual void trace(Visitor*) { }
 };
 
 class HTMLCanvasElement final : public HTMLElement, public DocumentVisibilityObserver, public CanvasImageSource, public ImageBufferClient {
@@ -150,8 +148,6 @@ public:
     virtual bool isDirty() override { return !m_dirtyRect.isEmpty(); }
     virtual void didFinalizeFrame() override;
 
-    virtual void trace(Visitor*) override;
-
 protected:
     virtual void didMoveToNewDocument(Document& oldDocument) override;