Have Document::accessSVGExtensions() return a reference

Source/core/svg/SVGUseElement.cpp

Index: Source/core/svg/SVGUseElement.cpp
diff --git a/Source/core/svg/SVGUseElement.cpp b/Source/core/svg/SVGUseElement.cpp
index b9b74d13e86fd8c42c260c98c4f47f471fcbe023..70f9169bb6b44a5900329074107a4b6b902f4bd5 100644
--- a/Source/core/svg/SVGUseElement.cpp
+++ b/Source/core/svg/SVGUseElement.cpp
@@ -374,7 +374,7 @@ void SVGUseElement::clearResourceReferences()
     m_needsShadowTreeRecreation = false;
     document().unscheduleUseShadowTreeUpdate(*this);
 
-    document().accessSVGExtensions()->removeAllTargetReferencesForElement(this);
+    document().accessSVGExtensions().removeAllTargetReferencesForElement(this);
 }
 
 void SVGUseElement::buildPendingResource()
@@ -395,7 +395,7 @@ void SVGUseElement::buildPendingResource()
         if (id.isEmpty())
             return;
 
-        referencedDocument()->accessSVGExtensions()->addPendingResource(id, this);
+        referencedDocument()->accessSVGExtensions().addPendingResource(id, this);
         ASSERT(hasPendingResources());
         return;
     }
@@ -534,7 +534,7 @@ void SVGUseElement::toClipPath(Path& path)
     if (n->isSVGElement() && toSVGElement(n)->isSVGGraphicsElement()) {
         if (!isDirectReference(n)) {
             // Spec: Indirect references are an error (14.3.5)
-            document().accessSVGExtensions()->reportError("Not allowed to use indirect reference in <clip-path>");
+            document().accessSVGExtensions().reportError("Not allowed to use indirect reference in <clip-path>");
         } else {
             toSVGGraphicsElement(n)->toClipPath(path);
             // FIXME: Avoid manual resolution of x/y here. Its potentially harmful.
@@ -574,7 +574,7 @@ void SVGUseElement::buildInstanceTree(SVGElement* target, SVGElementInstance* ta
         // We only need to track first degree <use> dependencies. Indirect references are handled
         // as the invalidation bubbles up the dependency chain.
         if (!foundUse) {
-            document().accessSVGExtensions()->addElementReferencingTarget(this, target);
+            document().accessSVGExtensions().addElementReferencingTarget(this, target);
             foundUse = true;
         }
     } else if (isDisallowedElement(target)) {