Allow Dart code to register service protocol handlers

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.
 ///
 library dart.developer;
 
 import 'dart:async';
 import 'dart:convert';
+import 'dart:isolate' show SendPort;
 
+part 'extension.dart';
 part 'profiler.dart';
 
 /// If [when] is true, stop the program as if a breakpoint were hit at the
 /// following statement.
 ///
 /// Returns the value of [when]. Some debuggers may display [message].
 ///
 /// NOTE: When invoked, the isolate will not return until a debugger
 /// continues execution. When running in the Dart VM the behaviour is the same
 /// regardless of whether or not a debugger is connected. When compiled to
@@ skipping 16 matching lines @@
 /// [error] (optional) an error object associated with this log event.
 /// [stackTrace] (optional) a stack trace associated with this log event.
 external log(String message,
              {DateTime time,
               int sequenceNumber,
               int level: 0,
               String name: '',
               Zone zone,
               Object error,
               StackTrace stackTrace});