message: [cli] Only inject custom-elements-es5-adapter.js when compiling to ES5
diff: @@ -53,7 +53,9 @@ export async function build(
  let buildStream: NodeJS.ReadableStream =
  mergeStream(sourcesStream, depsStream);
  - const compiledToES5 = !!(options.js && options.js.compile);
  + const compiledToES5 = (options.js === undefined) ?
  + false :
  + options.js.compile === true || options.js.compile === false;
  if (compiledToES5) {
  buildStream =
  buildStream.pipe(polymerProject.addCustomElementsEs5Adapter());
  