Fix the weird names that can occur in exceptions and logs when there is no

lib/unittest/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.
 /**
  * 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 {
   var _out;
 
-  /**
-   * Initialize the description with initial contents [init].
-   */
+  /** Initialize the description with initial contents [init]. */
   StringDescription([String init = '']) {
     _out = init;
   }
 
-  /**
-   * Get the description as a string.
-   */
+  /** Get the description as a string. */
   String toString() => _out;
 
-  /**
-   * Append some plain [text] to the description.
-   */
+  /** Append some plain [text] to the description.  */
   Description add(String text) {
     _out = '${_out}${text}';
     return this;
   }
 
+  /** Change the value of the description. */
+  Description replace(String 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".
    */
   Description addDescriptionOf(value) {
     if (value is Matcher) {
       value.describe(this);
     } else if (value is String) {
@@ skipping 47 matching lines @@
     else if (ch == '\n')
       return '\\n';
     else if (ch == '\r')
       return '\\r';
     else if (ch == '\t')
       return '\\t';
     else
       return ch;
   }
 }