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

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
===================================================================
--- runtime/include/dart_api.h	(revision 1518)
+++ runtime/include/dart_api.h	(working copy)
@@ -390,6 +390,15 @@
 const Dart_Port kCloseAllPorts = 0;
 
 /**
+ * A create port callback.
+ *
+ * This callback allows the embedder to receive notification when a
+ * port is created.
+ */
+typedef void (*Dart_CreatePortCallback)(Dart_Isolate isolate,
+                                        Dart_Port port);
+
+/**
  * A close port callback.
  *
  * This callback allows the embedder to receive notification when a
@@ -409,6 +418,7 @@
  * execution begins, the embedder is responsible for threading issues.
  */
 DART_EXPORT void Dart_SetMessageCallbacks(
+    Dart_CreatePortCallback create_port_callback,
     Dart_PostMessageCallback post_message_callback,
     Dart_ClosePortCallback close_port_callback);
 // TODO(turnidge): Consider moving this to isolate creation so that it
@@ -445,6 +455,16 @@
 // TODO(turnidge): Should this be removed from the public api?
 
 /**
+ * Creates a Dart_Port and associates it with the current isolate.
+ */
+DART_EXPORT Dart_Port Dart_CreatePort();
+
+/**
+ * Does the current isolate have active ports?
+ */
+DART_EXPORT bool Dart_IsolateHasActivePorts();
+
+/**
  * Posts a message for some isolate. The message is built from a raw
  * array.
  *