Update the analysis server diagnostic page - re-enable code completion and overlay pages,

pkg/analyzer/lib/src/dart/analysis/file_state.dart

 // Copyright (c) 2016, 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:typed_data';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 46 matching lines @@
    *
    * The [path] must be absolute and normalized.
    */
   void operator []=(String path, String content) {
     if (content == null) {
       _map.remove(path);
     } else {
       _map[path] = content;
     }
   }
+
+  /**
+   * Return the paths currently being overridden.
+   */
+  Iterable<String> get paths => _map.keys;
 }
 
 /**
  * Information about a file being analyzed, explicitly or implicitly.
  *
  * It provides a consistent view on its properties.
  *
  * The properties are not guaranteed to represent the most recent state
  * of the file system. To update the file to the most recent state, [refresh]
  * should be called.
@@ skipping 849 matching lines @@
   _FastaElementProxy operator [](fasta.Builder builder) =>
       _elements.putIfAbsent(builder, () => new _FastaElementProxy());
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
 class _FastaInterfaceTypeProxy implements fasta.KernelInterfaceType {
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }