Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/svg/SVGElement.cpp

Index: Source/core/svg/SVGElement.cpp
diff --git a/Source/core/svg/SVGElement.cpp b/Source/core/svg/SVGElement.cpp
index 177596b8771e19e5bf464450187f3ca20c29720a..de9bc09e2cf9e98a3e6a83a12cf7dc95a73d500c 100644
--- a/Source/core/svg/SVGElement.cpp
+++ b/Source/core/svg/SVGElement.cpp
@@ -114,9 +114,12 @@ SVGElement::~SVGElement()
         // removeAllElementReferencesForTarget() below.
         clearHasSVGRareData();
     }
-#endif
+
+    // With Oilpan, either removedFrom has been called or the document is dead
+    // as well and there is no reason to clear out the extensions.
     document().accessSVGExtensions().rebuildAllElementReferencesForTarget(this);
     document().accessSVGExtensions().removeAllElementReferencesForTarget(this);
+#endif
 }
 
 void SVGElement::willRecalcStyle(StyleRecalcChange change)