Big merge from experimental to bleeding edge.

sdk/lib/core/errors.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.
 
 part of dart.core;
 
 class Error {
   const Error();
 
   /**
@@ skipping 178 matching lines @@
           "Tried calling: $_memberName($actualParameters)\n"
           "Found: $_memberName($formalParameters)";
     }
   }
 }
 
 
 /**
  * The operation was not allowed by the object.
  *
- * This [Error] is thrown when a class cannot implement
- * one of the methods in its signature.
+ * This [Error] is thrown when an instance cannot implement one of the methods
+ * in its signature.
  */
 class UnsupportedError implements Error {
   final String message;
   UnsupportedError(this.message);
   String toString() => "Unsupported operation: $message";
 }
 
 
 /**
  * Thrown by operations that have not been implemented yet.
@@ skipping 38 matching lines @@
 }
 
 /**
  * Error thrown when a runtime error occurs.
  */
 class RuntimeError implements Error {
   final message;
   RuntimeError(this.message);
   String toString() => "RuntimeError: $message";
 }