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* Interface with constants for the different request destinations that are supported.
* For the purposes of the AMP implementation, we are only interested in the
* request destinations that are valid values for the 'as' attribute in preloads.
* Full list of request destinations:
* @see https://fetch.spec.whatwg.org/#concept-request-destination
* @package ampproject/amp-toolbox
interface RequestDestination
* Audio file, as typically used in <audio>.
* An HTML document intended to be embedded by a <frame> or <iframe>.
const DOCUMENT = 'document';
* A resource to be embedded inside an <embed> element.
* Resource to be accessed by a fetch or XHR request, such as an ArrayBuffer or JSON file.
* A resource to be embedded inside an <object> element.
* A JavaScript web worker or shared worker.
* Video file, as typically used in <video>.