Including "rewrite_polyfills=false" in parameters to web service has no affect.

When I POST a request to https://closure-compiler.appspot.com/compile with "rewrite_polyfills=false" included, it appears to be ignored.

`["output_format=json", "compilation_level=SIMPLE_OPTIMIZATIONS", "language=ECMASCRIPT8", "rewrite_polyfills=false", "output_info=compiled_code", "output_info=statistics", "output_info=errors", "output_info=warnings", "code_url=https://<>"]`

Same behavior when I try using the web page manually and add @rewrite_polyfills false

`
// ==ClosureCompiler==

// @compilation_level SIMPLE_OPTIMIZATIONS
// @output_file_name default.js
// **@rewrite_polyfills false**
// @code_url https://<>
// ==/ClosureCompiler==
`

Tellingly, in this case, the POST DATA tab doesn't show that parameter included.

Can we get this parameter supported in the web service?

Reproduce the POST and web-page requests described in the issue, then trace how the web service handles the rewrite_polyfills parameter. Done means the parameter is retained in the POST data and changes compilation behavior when set to false.

Written by the indexing model from the issue text.