Add a mid-sized integration test for the Dart Embedding Api which

runtime/lib/isolate.dart

Index: runtime/lib/isolate.dart
===================================================================
--- runtime/lib/isolate.dart	(revision 1762)
+++ runtime/lib/isolate.dart	(working copy)
@@ -18,12 +18,14 @@
   factory ReceivePortImpl() native "ReceivePortImpl_factory";
 
   receive(void onMessage(var message, SendPort replyTo)) {
+    _numLivePorts++;

[siva, 2011/11/24 00:52:31]

If I call receive multiple times on the same receive port then will I end up
with my numLivePorts being off.
e.g:
port.receive(handler1);
port.receive(handler2);
port.receive(null);

Maybe you should increment only if _onMessage is null and decrement if
_onMessage is set to null

[turnidge, 2011/11/29 01:01:31]

I redid the change so that isolate.dart doesn't need to change.  Instead I keep
track of the live ports on the C++ side.  I have also changed the definition of
"live" from "has a non-null handler" to "has a ReceivePort created for it".  I
did this because of an offline discussion about what the meaning of "null" for a
handler should be.

     _onMessage = onMessage;
   }
 
   close() {
     _portMap.remove(_id);
     _closeInternal(_id);
+    _numLivePorts--;
   }
 
   SendPort toSendPort() {
@@ -32,18 +34,21 @@
 
   /**** Internal implementation details ****/
   // Called from the VM to create a new ReceivePort instance.
-  static ReceivePortImpl create_(int id) {
+  static ReceivePortImpl _create(int id) {
     return new ReceivePortImpl._internal(id);
   }
   ReceivePortImpl._internal(int id) : _id = id {
     if (_portMap === null) {
       _portMap = new Map();
+      _numLivePorts = 0;
     }
     _portMap[id] = this;
   }
 
+  static int _getNumLivePorts() => _numLivePorts === null ? 0 : _numLivePorts;
+
   // Called from the VM to dispatch to the handler.
-  static void handleMessage_(int id, int replyId, var message) {
+  static void _handleMessage(int id, int replyId, var message) {
     assert(_portMap !== null);
     ReceivePort port = _portMap[id];
     SendPort replyTo = (replyId == 0) ? null : new SendPortImpl(replyId);
@@ -58,6 +63,9 @@
 
   // id to ReceivePort mapping.
   static Map _portMap;
+
+  // The number of ReceivePorts which have called receive.
+  static int _numLivePorts;
 }
 
 
@@ -119,9 +127,9 @@
   /*--- private implementation ---*/
   const SendPortImpl(int id) : _id = id;
 
-  // SendPortImpl.create_ is called from the VM when a new SendPort instance is
+  // SendPortImpl._create is called from the VM when a new SendPort instance is
   // needed by the VM code.
-  static SendPort create_(int id) {
+  static SendPort _create(int id) {
     return new SendPortImpl(id);
   }