Add @overrides to (a lot of) analyzer.

pkg/analyzer/lib/src/generated/source_io.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.src.generated.source_io;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_core.dart';
@@ skipping 84 matching lines @@
    * identifier is used for equality tests and hash codes.
    *
    * The URI and filepath are joined into a pair by separating them with an '@'
    * character.
    */
   static final Map<String, int> _idTable = new HashMap<String, int>();
 
   /**
    * The URI from which this source was originally derived.
    */
+  @override
   final Uri uri;
 
   /**
    * The unique ID associated with this [FileBasedSource].
    */
   final int id;
 
   /**
    * The file represented by this source.
    */
@@ skipping 423 matching lines @@
   }
 
   /**
    * Return `true` if the given URI is a `file` URI.
    *
    * @param uri the URI being tested
    * @return `true` if the given URI is a `file` URI
    */
   static bool isFileUri(Uri uri) => uri.scheme == FILE_SCHEME;
 }