Remove public dart:isolate dependency from dart:developer

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';
 part 'timeline.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].
 ///
@@ skipping 19 matching lines @@
 /// [error]  (optional) an error object associated with this log event.
 /// [stackTrace]  (optional) a stack trace associated with this log event.
 external void log(String message,
                   {DateTime time,
                    int sequenceNumber,
                    int level: 0,
                    String name: '',
                    Zone zone,
                    Object error,
                    StackTrace stackTrace});