Re-organize and comment clean-up

pkg/analyzer_plugin/lib/plugin/plugin.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 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/byte_store.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart'
     show AnalysisDriverScheduler, PerformanceLog;
 import 'package:analyzer/src/dart/analysis/file_byte_store.dart';
 import 'package:analyzer/src/dart/analysis/file_state.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer_plugin/channel/channel.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart';
 import 'package:analyzer_plugin/protocol/protocol_constants.dart';
 import 'package:analyzer_plugin/protocol/protocol_generated.dart';
 import 'package:analyzer_plugin/src/protocol/protocol_internal.dart';
 import 'package:analyzer_plugin/src/utilities/null_string_sink.dart';
-import 'package:analyzer_plugin/utilities/subscription_manager.dart';
+import 'package:analyzer_plugin/utilities/subscriptions/subscription_manager.dart';
 import 'package:pub_semver/pub_semver.dart';
 
 /**
  * The abstract superclass of any class implementing a plugin for the analysis
  * server.
  *
  * Clients may not implement or mix-in this class, but are expected to extend
  * it.
  */
 abstract class ServerPlugin {
@@ skipping 367 matching lines @@
       response = new Response(id,
           error: new RequestError(
               RequestErrorCode.PLUGIN_ERROR, exception.toString(),
               stackTrace: stackTrace.toString()));
     }
     if (response != null) {
       _channel.sendResponse(response);
     }
   }
 }