* IllegalArgumentException, since the call could succeed with a different argument. Those
     * exceptions' docs suggest that either is acceptable. Google's Java Practices page recommends
     * IllegalArgumentException here, in part to keep its recommendation simple: Static methods
     * should throw IllegalStateException only when they use static state.
     *

    to the call and can adjust all call timeouts. Note that this change is
    source-incompatible for code that implements the `Chain` interface.
    We don't expect this to be a problem in practice!

 *  **OkHttp has an experimental new API for tracking metrics.** The new
    `EventListener` API is designed to help developers monitor HTTP requests'

 *
 * Username and password are either present, or the empty string `""` if absent. This class offers
 * no mechanism to differentiate empty from absent. Neither of these components are popular in
 * practice. Typically HTTP applications use other mechanisms for user identification and
 * authentication.
 *
 * ### Host
 *
 * The host identifies the webserver that serves the URL's resource. It is either a hostname like