Let completers complete in the zone they were constructed in.

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 be0b7a23229fff9d0acee3ff592698f11332e542..738a9bba9aa368a0f5ce12bbac26820c7118fe2d 100644
--- a/sdk/lib/async/future_impl.dart
+++ b/sdk/lib/async/future_impl.dart
@@ -10,9 +10,11 @@ deprecatedFutureValue(_FutureImpl future) =>
 abstract class _Completer<T> implements Completer<T> {
   final Future<T> future;

[Anders Johnsen, 2013/07/05 17:10:50]

It's okay to type this _FutureImpl, and then avoid the casts in the methods, as
this is not exposed (it's the private _Completer).

[floitsch, 2013/07/05 18:08:19]

I think I once had a _FutureImpl here, but Lasse asked me to change it.

[Lasse Reichstein Nielsen, 2013/07/05 18:49:43]

The argument was that is that the field is public, and I want it to match the
signature of Completer.

It may be irrelevant, since both this class and _FutureImpl are private, so it's
not like you can see a difference without mirrors, and with mirrors you can see
everything anyway.

   bool _isComplete = false;
+  final _Zone _zone = _Zone.current.fork();
 
   _Completer() : future = new _FutureImpl<T>() {

[Anders Johnsen, 2013/07/05 17:10:50]

So Future have a Zone too, so why not just use that zone? As it's constructed
just like here, they'll follow each other (actually be precisely the same)?

[floitsch, 2013/07/05 18:08:19]

Right...
No need for Zones in the completer. Removed.

[Lasse Reichstein Nielsen, 2013/07/05 18:49:43]

My interpretation too. Can't you just use future._zone?

[floitsch, 2013/07/05 18:51:46]

Completer.zone is already removed.

     _FutureImpl futureImpl = future;
+    _zone.expectCallback();
     futureImpl._zone.expectCallback();
   }
 
@@ -23,6 +25,7 @@ abstract class _Completer<T> implements Completer<T> {
     if (_isComplete) throw new StateError("Future already completed");
     _isComplete = true;
     _FutureImpl futureImpl = future;
+    _zone.cancelCallbackExpectation();
     futureImpl._zone.cancelCallbackExpectation();
     _setFutureValue(value);
   }
@@ -35,11 +38,13 @@ abstract class _Completer<T> implements Completer<T> {
       _attachStackTrace(error, stackTrace);
     }
     _FutureImpl futureImpl = future;
-    if (futureImpl._inSameErrorZone(_Zone.current)) {
+    if (futureImpl._inSameErrorZone(_zone)) {

[Anders Johnsen, 2013/07/05 17:10:50]

futureImpl._zone and below?

[floitsch, 2013/07/05 18:08:19]

Actually it must be the same zone now, so I could remove the test.

+      _zone.cancelCallbackExpectation();
       futureImpl._zone.cancelCallbackExpectation();
       _setFutureError(error);
     } else {
-      _Zone.current.handleUncaughtError(error);
+      _zone.cancelCallbackExpectation();
+      _zone.handleUncaughtError(error);
     }
   }