Make instrumentation data structure more regular

pkg/analyzer/lib/instrumentation/instrumentation.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.instrumentation.instrumentation;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/task/model.dart';
@@ skipping 219 matching lines @@
         _toString(exception),
         _toString(stackTrace)
       ];
       plugin.addToFields(fields);
       _instrumentationServer.log(_join(fields));
     }
   }
 
   void logPluginNotification(String pluginId, String notification) {
     if (_instrumentationServer != null) {
-      _instrumentationServer
-          .log(_join([TAG_PLUGIN_NOTIFICATION, pluginId, notification]));
+      _instrumentationServer.log(
+          _join([TAG_PLUGIN_NOTIFICATION, notification, pluginId, '', '']));
     }
   }
 
   void logPluginRequest(String pluginId, String request) {
     if (_instrumentationServer != null) {
       _instrumentationServer
-          .log(_join([TAG_PLUGIN_REQUEST, pluginId, request]));
+          .log(_join([TAG_PLUGIN_REQUEST, request, pluginId, '', '']));
     }
   }
 
   void logPluginResponse(String pluginId, String response) {
     if (_instrumentationServer != null) {
       _instrumentationServer
-          .log(_join([TAG_PLUGIN_RESPONSE, pluginId, response]));
+          .log(_join([TAG_PLUGIN_RESPONSE, response, pluginId, '', '']));
     }
   }
 
   /**
    * Log that the given [plugin] took too long to execute the given [request].
+   * This doesn't necessarily imply that there is a problem with the plugin,
+   * only that this particular response was not included in the data returned
+   * to the client.
    */
   void logPluginTimeout(PluginData plugin, String request) {
     if (_instrumentationServer != null) {
       List<String> fields = <String>[TAG_PLUGIN_TIMEOUT, request];
       plugin.addToFields(fields);
       _instrumentationServer.log(_join(fields));
     }
   }
 
   /**
@@ skipping 223 matching lines @@
    * Initialize a newly created set of data about a plugin.
    */
   PluginData(this.pluginId, this.name, this.version);
 
   /**
    * Add the information about the plugin to the list of [fields] to be sent to
    * the instrumentation server.
    */
   void addToFields(List<String> fields) {
     fields.add(pluginId);
-    if (name != null) {
-      fields.add(name);
-    }
-    if (version != null) {
-      fields.add(version);
-    }
+    fields.add(name ?? '');
+    fields.add(version ?? '');
   }
 }