Add Future.timeout.

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 90e9df2b5033586837a245375526a067e24a7805..78bc979a8a831303a647b786bbc5010bfadb7897 100644
--- a/sdk/lib/async/future_impl.dart
+++ b/sdk/lib/async/future_impl.dart
@@ -537,4 +537,34 @@ class _Future<T> implements Future<T> {
       source = listener;
     }
   }
+
+  Future timeout(Duration timeLimit, onTimeout()) {
+    if (_isComplete) return new _Future.immediate(this);
+    Zone zone = Zone.current;
+    onTimeout = zone.registerCallback(onTimeout);
+    _Future result = new _Future();
+    bool completeNormally = true;
+    Timer timer = new Timer(timeLimit, () {
+      completeNormally = false;
+      zone.run(() {

[floitsch, 2013/11/27 12:31:16]

I think it would be nicer if you passed "onTimeout" to the zone.
so:
try {
  result._complete(zone.run(onTimeout));
} catch (e, s) {
  result._completeError(e, s);
}

This way the zone gets the function that was registered.

[Lasse Reichstein Nielsen, 2013/11/27 12:54:20]

Good point. Done.

+        try {
+          result._complete(onTimeout());
+        } catch (e, s) {
+          result._completeError(e, s);
+        }
+      });
+    });
+    this.then((T v) {
+      if (completeNormally) {
+        timer.cancel();
+        result._complete(v);
+      }
+    }, onError: (e, s) {
+      if (completeNormally) {
+        timer.cancel();
+        result._completeError(e, s);
+      }
+    });
+    return result;
+  }
 }