Roll Observatory packages and add a roll script

analyzer/lib/src/generated/interner.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 interner;
-
-import 'dart:collection';
-
-/**
- * The interface `Interner` defines the behavior of objects that can intern
- * strings.
- */
-abstract class Interner {
-  /**
-   * Return a string that is identical to all of the other strings that have
-   * been interned that are equal to the given [string].
-   */
-  String intern(String string);
-}
-
-/**
- * The class `MappedInterner` implements an interner that uses a map to manage
- * the strings that have been interned.
- */
-class MappedInterner implements Interner {
-  /**
-   * A table mapping strings to themselves.
-   */
-  Map<String, String> _table = new HashMap<String, String>();
-
-  @override
-  String intern(String string) {
-    String original = _table[string];
-    if (original == null) {
-      _table[string] = string;
-      return string;
-    }
-    return original;
-  }
-}
-
-/**
- * The class `NullInterner` implements an interner that does nothing (does not
- * actually intern any strings).
- */
-class NullInterner implements Interner {
-  @override
-  String intern(String string) => string;
-}