New OutputStream interface

tests/standalone/src/ProcessStdoutTest.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Process test program to test process communication.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
@@ skipping 31 matching lines @@
       }
 
       void streamClosed() {
         Expect.equals(BUFFERSIZE, received);
       }
 
       input.dataHandler = readData;
       input.closeHandler = streamClosed;
     }
 
-    bool written = output.write(data, 0, BUFFERSIZE, dataWritten);
-    if (written) {
-      dataWritten();
-    }
+    output.write(data);
+    dataWritten();
   }
 
   static void testMain() {
     testStdout();
   }
 }
 
 main() {
   ProcessStdoutTest.testMain();
 }