Prepare SVGDocumentExtensions::m_elementDependencies for oilpan

Source/core/svg/SVGPathElement.cpp

Index: Source/core/svg/SVGPathElement.cpp
diff --git a/Source/core/svg/SVGPathElement.cpp b/Source/core/svg/SVGPathElement.cpp
index bc9bb19a05c68aa4e85c40b7ef756136aefdee9a..9ad7766ed80b2ace03eda27b2b92785b9ada6006 100644
--- a/Source/core/svg/SVGPathElement.cpp
+++ b/Source/core/svg/SVGPathElement.cpp
@@ -234,9 +234,9 @@ void SVGPathElement::invalidateMPathDependencies()
 {
     // <mpath> can only reference <path> but this dependency is not handled in
     // markForLayoutAndParentResourceInvalidation so we update any mpath dependencies manually.
-    if (HashSet<SVGElement*>* dependencies = document().accessSVGExtensions().setOfElementsReferencingTarget(this)) {
-        HashSet<SVGElement*>::iterator end = dependencies->end();
-        for (HashSet<SVGElement*>::iterator it = dependencies->begin(); it != end; ++it) {
+    if (WeakSVGElementSet* dependencies = document().accessSVGExtensions().setOfElementsReferencingTarget(this)) {
+        WeakSVGElementSet::iterator end = dependencies->end();
+        for (WeakSVGElementSet::iterator it = dependencies->begin(); it != end; ++it) {
             if (isSVGMPathElement(**it))
                 toSVGMPathElement(*it)->targetPathChanged();
         }