Improve the documentation of logRequests().

lib/src/handlers/logger.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:stack_trace/stack_trace.dart';
 
 import '../hijack_exception.dart';
 import '../middleware.dart';
 
 /// Middleware which prints the time of the request, the elapsed time for the
 /// inner handlers, the response's status code and the request URI.
 ///
-/// [logger] takes two parameters.
+/// If [logger] is passed, it's called for each request. The `msg` parameter is
+/// a formatted string that includes the request time, duration, request method,
+/// and requested path. When an exception is thrown, it also includes the
+/// exception's string and stack trace; otherwise, it includes the status code.
+/// The `isError` parameter indicates whether the message is caused by an error.
 ///
-/// `msg` includes the request time, duration, request method, and requested
-/// path.
-///
-/// For successful requests, `msg` also includes the status code.
-///
-/// When an error is thrown, `isError` is true and `msg` contains the error
-/// description and stack trace.
+/// If [logger] is not passed, the message is just passed to [print].
 Middleware logRequests({void logger(String msg, bool isError)}) =>
     (innerHandler) {
   if (logger == null) logger = _defaultLogger;
 
   return (request) {
     var startTime = new DateTime.now();
     var watch = new Stopwatch()..start();
 
     return new Future.sync(() => innerHandler(request)).then((response) {
       var msg = _getMessage(startTime, response.statusCode,
@@ skipping 40 matching lines @@
   return '$msg\n$chain';
 }
 
 void _defaultLogger(String msg, bool isError) {
   if (isError) {
     print('[ERROR] $msg');
   } else {
     print(msg);
   }
 }