Implement a replacement for FileBasedSource (and _MemoryFileSource)

pkg/analyzer/test/src/test_all.dart

Index: pkg/analyzer/test/src/test_all.dart
diff --git a/pkg/analyzer/test/src/test_all.dart b/pkg/analyzer/test/src/test_all.dart
index c92adfa001126bf38f130aede8401f0add22043e..94cbace14dffc686e58d94b49614a6436ae6a77c 100644
--- a/pkg/analyzer/test/src/test_all.dart
+++ b/pkg/analyzer/test/src/test_all.dart
@@ -10,6 +10,7 @@ import '../utils.dart';
 import 'context/test_all.dart' as context;
 import 'dart/test_all.dart' as dart;
 import 'plugin/plugin_config_test.dart' as plugin;
+import 'source/test_all.dart' as source;
 import 'summary/test_all.dart' as summary;
 import 'task/test_all.dart' as task;
 import 'util/test_all.dart' as util;
@@ -21,6 +22,7 @@ main() {
     context.main();
     dart.main();
     plugin.main();
+    source.main();
     summary.main();
     task.main();
     util.main();