Remove deprecated parts of dart:async.

sdk/lib/async/future_impl.dart

Index: sdk/lib/async/future_impl.dart
diff --git a/sdk/lib/async/future_impl.dart b/sdk/lib/async/future_impl.dart
index 178445838e37bb7e1445cb5435e6eed2f228a763..96ee31a00429edf2b9f1a42346b5947b75e6f062 100644
--- a/sdk/lib/async/future_impl.dart
+++ b/sdk/lib/async/future_impl.dart
@@ -309,11 +309,6 @@ class _Future<T> implements Future<T> {
     assert(_whenCompleteAction == null);
     assert(_errorTest == null);
 
-    if (stackTrace != null) {
-      // Force the stack trace onto the error, even if it already had one.
-      _attachStackTrace(error, stackTrace);
-    }
-
     _Future listeners = _isChained ? null : _removeListeners();
     _setError(error, stackTrace);
     _propagateToListeners(this, listeners);
@@ -507,7 +502,7 @@ class _Future<T> implements Future<T> {
           if (hasError && identical(source._error.error, e)) {
             listenerValueOrError = source._error;
           } else {
-            listenerValueOrError = new _AsyncError(_asyncError(e, s), s);
+            listenerValueOrError = new _AsyncError(e, s);
           }
           listenerHasValue = false;
         }