Revert changes to Future.chain() and Future.transform() from http://codereview.chromium.org/10517006

corelib/src/future.dart

 // Copyright (c) 2011, 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.
 
 // Dart core library.
 
 
 /**
  * A [Future] is used to obtain a value sometime in the future.  Receivers of a
  * [Future] can obtain the value by passing a callback to [then].
@@ skipping 79 matching lines @@
   void handleException(bool onException(Object exception));
 
   /**
    * A future representing [transformation] applied to this future's value.
    *
    * When this future gets a value, [transformation] will be called on the
    * value, and the returned future will receive the result.
    *
    * If an exception occurs (received by this future, or thrown by
    * [transformation]) then the returned future will receive the exception.
+   *  
+   * You must not add exception handlers to [this] future prior to calling 
+   * transform, and any you add afterwards will not be invoked.
    */
   Future transform(transformation(T value));
 
    /**
     * A future representing an asynchronous transformation applied to this
     * future's value. [transformation] must return a Future.
     *
     * When this future gets a value, [transformation] will be called on the
     * value. When the resulting future gets a value, the returned future
     * will receive it.
     *
     * If an exception occurs (received by this future, thrown by
     * [transformation], or received by the future returned by [transformation])
     * then the returned future will receive the exception.
+    *
+    * You must not add exception handlers to [this] future prior to calling 
+    * chain, and any you add afterwards will not be invoked.
     */
    Future chain(Future transformation(T value));
 }
 
 
 /**
  * A [Completer] is used to produce [Future]s and supply their value when it
  * becomes available.
  *
  * A service that provides values to callers, and wants to return [Future]s can
@@ skipping 81 matching lines @@
         }
       });
       future.handleException((exception) {
         if (!result.isComplete) completer.completeException(exception);
         return true;
       });
     }
     return result;
   }
 }