Add instrumentation data to the analysis server diagnostics page.

pkg/analyzer/lib/instrumentation/file_instrumentation.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.
 
 library analyzer.instrumentation.file_instrumentation;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:analyzer/instrumentation/instrumentation.dart';
 
 /**
  * An [InstrumentationServer] that writes to a file.
  */
 class FileInstrumentationServer implements InstrumentationServer {
+  final String filePath;
   IOSink _sink;
 
-  FileInstrumentationServer(String path) {
-    File file = new File(path);
+  FileInstrumentationServer(this.filePath) {
+    File file = new File(filePath);
     _sink = file.openWrite();
   }
 
   @override
   String get sessionId => '';
 
   @override
+  String get describe => "file: $filePath, session $sessionId";

[Brian Wilkerson, 2017/02/27 14:41:32]

Not sure it's useful to print the session id given that it's always an empty
string.

[devoncarew, 2017/03/01 01:51:32]

updated to not use session

+
+  @override
   void log(String message) {
     _sink.writeln(message);
   }
 
   @override
   void logWithPriority(String message) {
     log(message);
   }
 
   @override
   Future shutdown() async {
     await _sink.close();
     _sink = null;
   }
 }