Make dart:developer log more user friendly

sdk/lib/developer/developer.dart

 // Copyright (c) 2015, 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.
 
 /// Interact with developer tools such as the debugger and inspector.
 ///
 /// The dart:developer library is _unstable_ and its API might change slightly
 /// as a result of developer feedback. This library is platform dependent and
 /// therefore it has implementations for both dart2js and the Dart VM. Both are
 /// under development and may not support all operations yet.
@@ skipping 16 matching lines @@
 /// JavaScript, this uses the "debugger" statement, and behaves exactly as
 /// that does.
 external bool debugger({bool when: true, String message});
 
 /// Send a reference to [object] to any attached debuggers.
 ///
 /// Debuggers may open an inspector on the object. Returns the argument.
 external Object inspect(Object object);
 
 /// Emit a log event.
-///
-/// [sequenceNumber] is a monotonically increasing sequence number.
-/// [millisececondsSinceEpoch] is a timestamp.
-/// [level] is the severity level (value between 0 and 2000 inclusive).
-/// [name] is the name of the source of the log message.
 /// [message] is the log message.
+/// [time] (optional) is the timestamp.
+/// [sequenceNumber] (optional) is a monotonically increasing sequence number.
+/// [level] (optional) is the severity level (value between 0 and 2000).
+/// [name] (optional) is the name of the source of the log message.
 /// [zone] (optional) the zone where the log was emitted
 /// [error] (optional) an error object associated with this log event.
 /// [stackTrace] (optional) a stack trace associated with this log event.
-external log({int sequenceNumber,
-              int millisecondsSinceEpoch,
-              int level,
-              String name,
-              String message,
+external log(String message,
+             {DateTime time,
+              int sequenceNumber,
+              int level: 0,
+              String name: '',
               Zone zone,
               Object error,
               StackTrace stackTrace});