futures: add more types to chain/transform, some additional cleanup.

corelib/src/implementation/future_implementation.dart

Index: corelib/src/implementation/future_implementation.dart
diff --git a/corelib/src/implementation/future_implementation.dart b/corelib/src/implementation/future_implementation.dart
index 48c7d405b7c0d58f31143d1268c6ac93c1d66a79..29bcbda7efda02937e6054ce5771d6dab85b9303 100644
--- a/corelib/src/implementation/future_implementation.dart
+++ b/corelib/src/implementation/future_implementation.dart
@@ -1,25 +1,6 @@
 // Copyright 2011 Google Inc. All Rights Reserved.
 // Dart core library.
 
-/**
- * Thrown if client tries to obtain value or exception
- * before a future has completed.
- */
-class FutureNotCompleteException implements Exception {
-  FutureNotCompleteException() {}
-  String toString() => "Exception: future has not been completed";
-}
-
-/**
- * Thrown if a completer tries to set the value on
- * a future that is already complete.
- */
-class FutureAlreadyCompleteException implements Exception {
-  FutureAlreadyCompleteException() {}
-  String toString() => "Exception: future already completed";
-}
-
-
 class FutureImpl<T> implements Future<T> {
 
   bool _isComplete;