Update dart:async to match the Dart repo.

tool/input_sdk/lib/async/async_error.dart

Index: tool/input_sdk/lib/async/async_error.dart
diff --git a/tool/input_sdk/lib/async/async_error.dart b/tool/input_sdk/lib/async/async_error.dart
index 9a640859b1247dd668c995fc5fa788bea8453703..2f3419e164fe023f4e844adfd3c0a9ec64bb420a 100644
--- a/tool/input_sdk/lib/async/async_error.dart
+++ b/tool/input_sdk/lib/async/async_error.dart
@@ -9,15 +9,18 @@ _invokeErrorHandler(Function errorHandler,
   if (errorHandler is ZoneBinaryCallback) {
     return errorHandler(error, stackTrace);
   } else {
-    return errorHandler(error);
+    ZoneUnaryCallback unaryErrorHandler = errorHandler;
+    return unaryErrorHandler(error);
   }
 }
 
-Function _registerErrorHandler(Function errorHandler, Zone zone) {
+Function _registerErrorHandler/*<R>*/(Function errorHandler, Zone zone) {
   if (errorHandler is ZoneBinaryCallback) {
-    return zone.registerBinaryCallback(errorHandler);
+    return zone.registerBinaryCallback/*<R, dynamic, StackTrace>*/(
+        errorHandler as dynamic/*=ZoneBinaryCallback<R, dynamic, StackTrace>*/);
   } else {
-    return zone.registerUnaryCallback(errorHandler);
+    return zone.registerUnaryCallback/*<R, dynamic>*/(
+        errorHandler as dynamic/*=ZoneUnaryCallback<R, dynamic>*/);
   }
 }