Add second argument to Future error handlers.

sdk/lib/async/async_error.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.async;
 
 final Expando _stackTraceExpando = new Expando("asynchronous error");
 
 void _attachStackTrace(o, st) {
   if (o == null || o is bool || o is num || o is String) return;
   _stackTraceExpando[o] = st;
 }
 
+_invokeErrorHandler(Function errorHandler,
+                    Object error, StackTrace stackTrace) {
+  if (errorHandler is ZoneBinaryCallback) {
+    return errorHandler(error, stackTrace);
+  } else {
+    return errorHandler(error);
+  }
+}
+
+Function _registerErrorHandler(Function errorHandler, Zone zone) {
+  if (errorHandler is ZoneBinaryCallback) {
+    return zone.registerBinaryCallback(errorHandler);
+  } else {
+    return zone.registerUnaryCallback(errorHandler);
+  }
+}
+
 /**
  * *This is an experimental API.*
  *
  * Get the [StackTrace] attached to [o].
  *
  * If object [o] was thrown and caught in a dart:async method, a [StackTrace]
  * object was attached to it. Use [getAttachedStackTrace] to get that object.
  *
  * Returns [null] if no [StackTrace] was attached.
  */
 getAttachedStackTrace(o) {
   if (o == null || o is bool || o is num || o is String) return null;
   return _stackTraceExpando[o];
 }
+
+class _AsyncError implements Error {
+  final error;
+  final StackTrace stackTrace;
+
+  _AsyncError(this.error, this.stackTrace);
+}
+
+class _UncaughtAsyncError extends _AsyncError {
+  _UncaughtAsyncError(error, StackTrace stackTrace)
+      : super(error, _getBestStackTrace(error, stackTrace)) {
+    // Clear the attached stack trace.
+    _attachStackTrace(error, null);
+  }
+
+  static StackTrace _getBestStackTrace(error, StackTrace stackTrace) {
+    if (stackTrace != null) return stackTrace;
+    var trace = getAttachedStackTrace(error);
+    if (trace != null) return trace;
+    if (error is Error) {
+      Error e = error;
+      return e.stackTrace;
+    }
+    return null;
+  }
+
+  String toString() {
+    String result = "Uncaught Error: ${error}";
+
+    if (stackTrace != null) {
+      result += "\nStack Trace:\n$stackTrace";
+    }
+    return result;
+  }
+}