Bug 1646140 - Fire SVG onload only when scripting is enabled. r=hsivonen, a=RyanVM

Differential Revision: https://phabricator.services.mozilla.com/D89218

parser/html/nsHtml5TreeBuilderCppSupplement.h

@@ -1072,6 +1072,9 @@ void nsHtml5TreeBuilder::elementPopped(int32_t aNamespace, nsAtom* aName,
   }
   if (aNamespace == kNameSpaceID_SVG) {
     if (aName == nsGkAtoms::svg) {
+      if (!scriptingEnabled || mPreventScriptExecution) {
+        return;
+      }
       if (mBuilder) {
         nsHtml5TreeOperation::SvgLoad(static_cast<nsIContent*>(aElement));
         return;