Fix source used in tests

pkg/analyzer/test/generated/test_support.dart

Index: pkg/analyzer/test/generated/test_support.dart
diff --git a/pkg/analyzer/test/generated/test_support.dart b/pkg/analyzer/test/generated/test_support.dart
index 5e6cfa42b723f7d806d432bfb19e510d3a1b3d30..51f5fcdc7b114455427e2e0cf937334fcbb4d0c0 100644
--- a/pkg/analyzer/test/generated/test_support.dart
+++ b/pkg/analyzer/test/generated/test_support.dart
@@ -6,8 +6,7 @@ library analyzer.test.generated.test_support;
 
 import 'dart:collection';
 
-import 'package:analyzer/dart/ast/ast.dart'
-    show AstNode, SimpleIdentifier;
+import 'package:analyzer/dart/ast/ast.dart' show AstNode, SimpleIdentifier;
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
@@ -647,6 +646,8 @@ class TestSourceWithUri extends TestSource {
   TestSourceWithUri(String path, this.uri, [String content])
       : super(path, content);
 
+  String get encoding => uri.toString();
+
   UriKind get uriKind {
     if (uri == null) {
       return UriKind.FILE_URI;