Oilpan: Prepare to move ImageLoader and its subclasses to Oilpan heap.

Source/core/svg/SVGImageElement.h

Index: Source/core/svg/SVGImageElement.h
diff --git a/Source/core/svg/SVGImageElement.h b/Source/core/svg/SVGImageElement.h
index 580a4d9b814baabd83504ea21f2dbc1af0b9870c..02806b6d7b1957597268aa0297fef972f16e0b0e 100644
--- a/Source/core/svg/SVGImageElement.h
+++ b/Source/core/svg/SVGImageElement.h
@@ -35,6 +35,7 @@ class SVGImageElement FINAL : public SVGGraphicsElement,
                               public SVGURIReference {
 public:
     DECLARE_NODE_FACTORY(SVGImageElement);
+    virtual void trace(Visitor*) OVERRIDE;
 
     bool currentFrameHasSingleSecurityOrigin() const;
 
@@ -66,6 +67,7 @@ private:
 
     virtual bool selfHasRelativeLengths() const OVERRIDE;
     virtual void didMoveToNewDocument(Document& oldDocument) OVERRIDE;
+    SVGImageLoader& imageLoader() { return *m_imageLoader; }
 
     RefPtr<SVGAnimatedLength> m_x;
     RefPtr<SVGAnimatedLength> m_y;
@@ -73,7 +75,7 @@ private:
     RefPtr<SVGAnimatedLength> m_height;
     RefPtr<SVGAnimatedPreserveAspectRatio> m_preserveAspectRatio;
 
-    SVGImageLoader m_imageLoader;
+    OwnPtrWillBeMember<SVGImageLoader> m_imageLoader;
     bool m_needsLoaderURIUpdate : 1;
 };