js: Name the optional argument for Container()
js: Name the optional argument for Container()

A future commit checks for invalid keys in the optional argument. To simplify
that, this commit names the optional argument parameter.

NetSys/quilt,kelda/kelda,kelda/kelda,kklin/quilt,quilt/quilt,kklin/quilt,NetSys/quilt,LuiseV/quilt,quilt/quilt,ejj/quilt-dev,kklin/kelda,NetSys/quilt,kklin/kelda,ejj/quilt-dev,LuiseV/quilt,kklin/kelda,ejj/quilt-dev,kklin/quilt,LuiseV/quilt,kelda/kelda,kklin/kelda,LuiseV/quilt,LuiseV/quilt,quilt/quilt,NetSys/quilt,quilt/quilt,ejj/quilt-dev,kelda/kelda,NetSys/quilt,kklin/quilt