pkg/matcher: Reverting 36881,36896 while investigating dart2js checked crash

pkg/matcher/lib/src/description.dart

 // Copyright (c) 2012, 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 matcher.description;
 
 import 'interfaces.dart';
 import 'pretty_print.dart';
+import 'utils.dart';
 
-/// The default implementation of [Description]. This should rarely need
-/// substitution, although conceivably it is a place where other languages
-/// could be supported.
+/**
+ * The default implementation of IDescription. This should rarely need
+ * substitution, although conceivably it is a place where other languages
+ * could be supported.
+ */
 class StringDescription implements Description {
-  final StringBuffer _out = new StringBuffer();
+  var _out;
 
-  /// Initialize the description with initial contents [init].
+  /** Initialize the description with initial contents [init]. */
   StringDescription([String init = '']) {
-    _out.write(init);
+    _out = init;
   }
 
   int get length => _out.length;
 
-  /// Get the description as a string.
-  String toString() => _out.toString();
+  /** Get the description as a string. */
+  String toString() => _out;
 
-  /// Append [text] to the description.
-  Description add(String text) {
-    _out.write(text);
+  /** Append [text] to the description.  */
+  Description add(text) {
+    _out = '${_out}${text}';
     return this;
   }
 
-  /// Change the value of the description.
+  /** Change the value of the description. */
   Description replace(String text) {
-    _out.clear();
-    return add(text);
+    _out = text;
+    return this;
   }
 
-  /// Appends a description of [value]. If it is an IMatcher use its
-  /// describe method; if it is a string use its literal value after
-  /// escaping any embedded control characters; otherwise use its
-  /// toString() value and wrap it in angular "quotes".
+  /**
+   * Appends a description of [value]. If it is an IMatcher use its
+   * describe method; if it is a string use its literal value after
+   * escaping any embedded control characters; otherwise use its
+   * toString() value and wrap it in angular "quotes".
+   */
   Description addDescriptionOf(value) {
     if (value is Matcher) {
       value.describe(this);
     } else {
       add(prettyPrint(value, maxLineLength: 80, maxItems: 25));
     }
     return this;
   }
 
-  /// Append an [Iterable] [list] of objects to the description, using the
-  /// specified [separator] and framing the list with [start]
-  /// and [end].
+  /**
+   * Append an [Iterable] [list] of objects to the description, using the
+   * specified [separator] and framing the list with [start]
+   * and [end].
+   */
   Description addAll(String start, String separator, String end,
                        Iterable list) {
     var separate = false;
     add(start);
     for (var item in list) {
       if (separate) {
         add(separator);
       }
       addDescriptionOf(item);
       separate = true;
     }
     add(end);
     return this;
   }
+
+  /** Escape the control characters in [string] so that they are visible. */
+  _addEscapedString(String string) {
+    add("'");
+    add(escapeString(string));
+    add("'");
+  }
 }