anchor.diff:  
     void addDoneListener(SendPort responsePort, Object response) {
       if (doneHandlers == null) {
  -      // TODO(lrn): Use map optimized for few keys.
  -      doneHandlers = new HashMap();
  -    }
  -    doneHandlers[responsePort] = response;
  +      doneHandlers = [];
  +    }
  +    for (int i = 0; i < doneHandlers.length; i += 2) {
  +      if (responsePort == doneHandlers[i]) {
  +        doneHandlers[i + 1] = response;
  +        return;
  +      }
  +    }
  +    doneHandlers.add(responsePort);
  +    doneHandlers.add(response);
     }
   
     void removeDoneListener(SendPort responsePort) {
       if (doneHandlers == null) return;
  -    doneHandlers.remove(responsePort);
  +    for (int i = 0; i < doneHandlers.length; i += 2) {
  +      if (responsePort == doneHandlers[i]) {
  +        doneHandlers.removeRange(i, i + 2);
  +        return;
  +      }
  +    }
     }
   
     void setErrorsFatal(Capability authentification, bool errorsAreFatal) {
  
positive.code:     INSTANCE_FROM_CLASS_ID;
  
  import 'dart:async';
  import 'dart:collection' show Queue, HashMap;
  import 'dart:isolate';
  import 'dart:_native_typed_data' show NativeByteBuffer, NativeTypedData;
  
  
negative.code:     _globalState.isolates.remove(id); // indicate this isolate is not active
      errorPorts.clear();
      if (doneHandlers != null) {
        for (int i = 0; i < doneHandlers.length; i += 2) {
          SendPort responsePort = doneHandlers[i];
          Object response = doneHandlers[i + 1];
          responsePort.send(response);
        }
        doneHandlers = null;
      }
    }
  