Add mirrors_reader_test.

tests/lib/mirrors/mirrors_reader_test.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.
+
+// Test that everything reachable from a [MirrorSystem] can be accessed.
+
+library test.mirrors.reader;
+
+import 'dart:mirrors';
+import 'mirrors_reader.dart';
+
+class RuntimeMirrorsReader extends MirrorsReader {
+  final String mirrorSystemType;
+
+  RuntimeMirrorsReader(MirrorSystem mirrorSystem)
+      : this.mirrorSystemType = '${mirrorSystem.runtimeType}';
+
+  bool allowUnsupported(var receiver, String tag, UnsupportedError exception) {
+    if (mirrorSystemType == '_LocalMirrorSystem') {
+      // VM mirror system.
+    } else if (mirrorSystemType == 'JsMirrorSystem') {
+      // Dart2js runtime mirror system.
+      if (tag.endsWith('.metadata')) {
+        return true;// Issue 10905.
+      }
+    }
+    return false;
+  }
+
+  bool expectUnsupported(var receiver, String tag, UnsupportedError exception) {
+    // [DeclarationMirror.location] is intentionally not supported in runtime
+    // mirrors.
+    if (receiver is DeclarationMirror && tag == 'location') {
+      return true;
+    }
+    if (mirrorSystemType == '_LocalMirrorSystem') {
+      // VM mirror system.
+    } else if (mirrorSystemType == 'JsMirrorSystem') {
+      // Dart2js runtime mirror system.
+    }
+    return false;
+  }
+}
+
+void main() {
+  MirrorSystem mirrors = currentMirrorSystem();
+  MirrorsReader reader = new RuntimeMirrorsReader(mirrors);
+  readMirrorSystem(reader, mirrors);
+}