Have Document::accessSVGExtensions() return a reference

Source/core/rendering/svg/ReferenceFilterBuilder.cpp

 /*
  * Copyright (C) 2013 Adobe Systems Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc.  All rights reserved.
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 112 matching lines @@
     }
 
     if (!document)
         return nullptr;
 
     Element* filter = document->getElementById(filterOperation->fragment());
 
     if (!filter) {
         // Although we did not find the referenced filter, it might exist later
         // in the document
-        document->accessSVGExtensions()->addPendingResource(filterOperation->fragment(), toElement(renderer->node()));
+        document->accessSVGExtensions().addPendingResource(filterOperation->fragment(), toElement(renderer->node()));
         return nullptr;
     }
 
     if (!filter->isSVGElement() || !filter->hasTagName(SVGNames::filterTag))
         return nullptr;
 
     SVGFilterElement* filterElement = toSVGFilterElement(toSVGElement(filter));
 
     // FIXME: Figure out what to do with SourceAlpha. Right now, we're
     // using the alpha of the original input layer, which is obviously
@@ skipping 23 matching lines @@
         effect->setEffectBoundaries(SVGLengthContext::resolveRectangle<SVGFilterPrimitiveStandardAttributes>(effectElement, filterElement->primitiveUnits()->currentValue()->enumValue(), parentFilter->sourceImageRect()));
         ColorSpace colorSpace = filterColorSpace;
         if (useFilterColorSpace || getSVGElementColorSpace(effectElement, colorSpace))
             effect->setOperatingColorSpace(colorSpace);
         builder->add(AtomicString(effectElement->result()->currentValue()->value()), effect);
     }
     return builder->lastEffect();
 }
 
 } // namespace WebCore