Fix bug in doWhile where it completes an error synchronously with an error.

sdk/lib/async/future.dart

Index: sdk/lib/async/future.dart
diff --git a/sdk/lib/async/future.dart b/sdk/lib/async/future.dart
index 25398426df6949709a6ace0d33d171cf283b6399..0368ae8220b162734c257fc8b8d7526e35440e2c 100644
--- a/sdk/lib/async/future.dart
+++ b/sdk/lib/async/future.dart
@@ -485,7 +485,9 @@ abstract class Future<T> {
         try {
           result = f();
         } catch (error, stackTrace) {
-          _completeWithErrorCallback(doneSignal, error, stackTrace);
+          // Cannot use _completeWithErrorCallback because it completes
+          // the future synchronously.
+          _asyncCompleteWithErrorCallback(doneSignal, error, stackTrace);
           return;
         }
         if (result is Future<bool>) {
@@ -873,5 +875,15 @@ void _completeWithErrorCallback(_Future result, error, stackTrace) {
   result._completeError(error, stackTrace);
 }
 
+// Like [_completeWIthErrorCallback] but completes asynchronously.

[eernst, 2017/04/06 11:45:57]

Typo: `WIth` --> `With`.

+void _asyncCompleteWithErrorCallback(_Future result, error, stackTrace) {
+  AsyncError replacement = Zone.current.errorCallback(error, stackTrace);
+  if (replacement != null) {
+    error = _nonNullError(replacement.error);
+    stackTrace = replacement.stackTrace;
+  }
+  result._asyncCompleteError(error, stackTrace);
+}
+
 /** Helper function that converts `null` to a [NullThrownError]. */
 Object _nonNullError(Object error) => error ?? new NullThrownError();