Add an OutputStream.closed getter.

runtime/bin/file_impl.dart

Index: runtime/bin/file_impl.dart
diff --git a/runtime/bin/file_impl.dart b/runtime/bin/file_impl.dart
index e1ff548fb669cfe7ba00be357490453da5ea5226..3e1f153f5c33b58eb0483d0d10844391d4e42604 100644
--- a/runtime/bin/file_impl.dart
+++ b/runtime/bin/file_impl.dart
@@ -217,13 +217,14 @@ class _FileOutputStream extends _BaseOutputStream implements OutputStream {
 

[Bill Hesse, 2012/08/08 14:21:11]

This will all need some work if we want writes after close() to throw
exceptions, instead of calling onError, but it is working as it was previously
this way, so OK.

 
   void close() {
+    _streamMarkedClosed = true;
     if (_file == null) {
       _pendingOperations.add(_PendingOperation.CLOSE);
-    } else if (!_streamMarkedClosed) {
+    } else if (!_closeCallbackCalled) {

[Bill Hesse, 2012/08/08 14:21:11]

Call this _closeCallbackScheduled.

[nweiz, 2012/08/09 19:39:52]

Done.

       _file.close().then((ignore) {
         if (_onClosed != null) _onClosed();
       });
-      _streamMarkedClosed = true;
+      _closeCallbackCalled = true;
     }
   }
 
@@ -279,6 +280,8 @@ class _FileOutputStream extends _BaseOutputStream implements OutputStream {
     });
   }
 
+  bool get closed() => _streamMarkedClosed;
+
   RandomAccessFile _file;
 
   // When this is set to true the stream is marked closed. When a