Implement spawnUri from dart:isolate. This function allows us to

runtime/lib/isolate.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.
 
 class _ReceivePortFactory {
   factory ReceivePort() {
     return new _ReceivePortImpl();
   }
 }
 
@@ skipping 112 matching lines @@
   }
 
   // Starts a new isolate calling the run method on a new instance of the
   // remote class's type.
   // Returns the send port which is passed to the newly created isolate.
   // This method is being dispatched to from the public core library code.
   static SendPort _start(Isolate isolate, bool light)
       native "IsolateNatives_start";
 }
 
 _getPortInternal() native "isolate_getPortInternal";

[Ivan Posva, 2012/05/15 00:04:46]

I must have missed this previously. Is there any reason why we went away from
the convention of "Class_method" for these native entry points?

[turnidge, 2012/05/15 17:47:38]

getPortInternal is a top-level function in the library "dart:isolate".  There
isn't a class name to use here...

 
 ReceivePort _portInternal;
 
 ReceivePort get _port() {
   if (_portInternal === null) {
     _portInternal = _getPortInternal();
   }
   return _portInternal;
 }
 
 _spawnFunction(void topLevelFunction()) native "isolate_spawnFunction";
 
-// TODO(sigmund,turnidge): implement
-SendPort _spawnUri(String uri) {
-  throw new NotImplementedException();
-}
+_spawnUri(String uri) native "isolate_spawnUri";