Bug 1494321 p1. Fix bug in PreEffectsVisualOverflowCollector::GetPreEffectsVisualOverflowRect. r=mattwoodrow

Differential Revision: https://phabricator.services.mozilla.com/D6987

--HG--
extra : rebase_source : eb0248f653adbd1c57c4b61d02ffdea615464069

layout/svg/nsSVGIntegrationUtils.cpp

@@ -104,7 +104,7 @@ private:
                  "GetVisualOverflowRect() won't return the pre-effects rect!");
     }
 #endif
-    return aFrame->GetVisualOverflowRect();
+    return aFrame->GetVisualOverflowRectRelativeToSelf();
   }
 
   nsIFrame*     mFirstContinuation;