Bug 1599296 - SVG images and links should not be draggable r=dholbert

Differential Revision: https://phabricator.services.mozilla.com/D55385

--HG--
extra : moz-landing-system : lando

dom/base/nsContentUtils.cpp

@@ -3429,6 +3429,9 @@ bool nsContentUtils::ContentIsDraggable(nsIContent* aContent) {
       return false;
     }
   }
+  if (aContent->IsSVGElement()) {
+    return false;
+  }
 
   // special handling for content area image and link dragging
   return IsDraggableImage(aContent) || IsDraggableLink(aContent);