Clean up some code in plugins

pkg/analyzer_plugin/lib/src/channel/isolate_channel.dart

 // Copyright (c) 2017, 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 'dart:convert';
 import 'dart:isolate';
 
 import 'package:analyzer/instrumentation/instrumentation.dart';
 import 'package:analyzer_plugin/channel/channel.dart';
@@ skipping 103 matching lines @@
       _subscription.cancel();
       _subscription = null;
     }
   }
 
   @override
   void listen(void onRequest(Request request),
       {Function onError, void onDone()}) {
     void onData(data) {
       Map<String, Object> requestMap = data;
-//      print('[plugin] Received request: ${JSON.encode(requestMap)}');
       Request request = new Request.fromJson(requestMap);
       if (request != null) {
         onRequest(request);
       }
     }
 
     if (_subscription != null) {
       throw new StateError('Only one listener is allowed per channel');
     }
     _subscription = _receivePort.listen(onData,
         onError: onError, onDone: onDone, cancelOnError: false);
   }
 
   @override
   void sendNotification(Notification notification) {
     Map<String, Object> json = notification.toJson();
-//    print('[plugin] Send notification: ${JSON.encode(json)}');
     _sendPort.send(json);
   }
 
   @override
   void sendResponse(Response response) {
     Map<String, Object> json = response.toJson();
-//    print('[plugin] Send response: ${JSON.encode(json)}');
     _sendPort.send(json);
   }
 }
 
 /**
  * A communication channel that allows an analysis server to send [Request]s
  * to, and to receive both [Response]s and [Notification]s from, a plugin.
  */
 abstract class ServerIsolateChannel implements ServerCommunicationChannel {
   /**
@@ skipping 128 matching lines @@
     String encodedRequest = JSON.encode(json);
     instrumentationService.logPluginRequest(pluginId, encodedRequest);
     _sendPort.send(json);
   }
 
   /**
    * Spawn the isolate in which the plugin is running.
    */
   Future<Isolate> _spawnIsolate();
 }