WebKit constructJSReadableStreamDefaultReader Type Confusion

WebKit: Type confusion in constructJSReadableStreamDefaultReader CVE-2017-2457 EncodedJSValue JSCHOSTCALL constructJSReadableStreamDefaultReaderExecState& exec VM& vm = exec.vm; auto scope = DECLARETHROWSCOPEvm; JSReadableStream stream = jsDynamicDowncastexec.argument0; if !stream return...