Oilpan: Reduce FIXME(OILPAN) from the code base

Source/core/layout/svg/LayoutSVGResourceLinearGradient.h

Index: Source/core/layout/svg/LayoutSVGResourceLinearGradient.h
diff --git a/Source/core/layout/svg/LayoutSVGResourceLinearGradient.h b/Source/core/layout/svg/LayoutSVGResourceLinearGradient.h
index 903f9dd3bf292ce5605c50269305218f13aa9bef..81cb59a65c271d9409b678cc5a748397fe9de439 100644
--- a/Source/core/layout/svg/LayoutSVGResourceLinearGradient.h
+++ b/Source/core/layout/svg/LayoutSVGResourceLinearGradient.h
@@ -48,10 +48,6 @@ public:
 
 private:
 #if ENABLE(OILPAN)
-    // FIXME: Oilpan: the LayoutObject hierarchy isn't on the heap, but
-    // the SVG property hierarchy is. And the two meet here, so keep a
-    // persistent reference to the SVG part object by way of a heap-allocated
-    // wrapper object.
     Persistent<LinearGradientAttributesWrapper> m_attributesWrapper;
 
     LinearGradientAttributes& mutableAttributes() { return m_attributesWrapper->attributes(); }