Have Document::accessSVGExtensions() return a reference

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 15eba686667bce8a5216514f8c8eeff9ecbb1d94..95226933fe070560c0a64ffe1a0677f8097c0355 100644
--- a/Source/core/svg/SVGPathElement.cpp
+++ b/Source/core/svg/SVGPathElement.cpp
@@ -212,7 +212,7 @@ void SVGPathElement::parseAttribute(const QualifiedName& name, const AtomicStrin
     } else if (name == SVGNames::pathLengthAttr) {
         m_pathLength->setBaseValueAsString(value, parseError);
         if (parseError == NoError && m_pathLength->baseValue()->value() < 0)
-            document().accessSVGExtensions()->reportError("A negative value for path attribute <pathLength> is not allowed");
+            document().accessSVGExtensions().reportError("A negative value for path attribute <pathLength> is not allowed");
     } else {
         ASSERT_NOT_REACHED();
     }
@@ -246,7 +246,7 @@ 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)) {
+    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 ((*it)->hasTagName(SVGNames::mpathTag))