core/modules/requestsMonitor/requestsMonitor.js
function lowerCaseHeaders(headers) {
	var res = {};

	Object.keys(headers).forEach(headerName => {
		res[headerName.toLowerCase()] = headers[headerName];
	});

	return res;
}
function lowerCaseHeaders(headers) {
	var res = {};

	Object.keys(headers).forEach(headerName => {
		res[headerName.toLowerCase()] = headers[headerName];
	});

	return res;
}
function lowerCaseHeaders ( headers ) { var res = { } ; Object . keys ( headers ) . forEach ( headerName => { res [ headerName . toLowerCase ( ) ] = headers [ headerName ] ; } ) ; return res ; }
Given key-value set of HTTP headers returns the set with lowercased header names

@param {object} headers
@returns {object}
Given key - value set of HTTP headers returns the set with lowercased header names