Bug 1543245 - Prevent HTML script tags from loading twice when using PrototypeDocument. r=smaug

HTML script tags were being loaded once by the element when it was bound
to the tree and a second time by the PrototypeDocumentContentSink. This
patch disables the script element from loading itself.

Depends on D26822

Differential Revision: https://phabricator.services.mozilla.com/D26823

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

dom/prototype/PrototypeDocumentContentSink.cpp

@@ -1034,6 +1034,15 @@ nsresult PrototypeDocumentContentSink::CreateElementFromPrototype(
 
     rv = AddAttributes(aPrototype, result);
     if (NS_FAILED(rv)) return rv;
+
+    if (xtfNi->Equals(nsGkAtoms::script, kNameSpaceID_XHTML) ||
+        xtfNi->Equals(nsGkAtoms::script, kNameSpaceID_SVG)) {
+      nsCOMPtr<nsIScriptElement> sele = do_QueryInterface(result);
+      MOZ_ASSERT(sele, "Node didn't QI to script.");
+      // Script loading is handled by the this content sink, so prevent the
+      // script from loading when it is bound to the document.
+      sele->PreventExecution();
+    }
   }
 
   result.forget(aResult);