lib/token-cache.js
function fireCallbacks(err, token) {
		self.pendingCallbacks.forEach(function (callback) {
			callback(err, token);
		});
		self.pendingCallbacks = [];
	}
function fireCallbacks(err, token) {
		self.pendingCallbacks.forEach(function (callback) {
			callback(err, token);
		});
		self.pendingCallbacks = [];
	}
function fireCallbacks ( err , token ) { self . pendingCallbacks . forEach ( function ( callback ) { callback ( err , token ) ; } ) ; self . pendingCallbacks = [ ] ; }
execute accumulated callbacks during the 'pending' state
execute accumulated callbacks during the pending state