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

runtime/vm/isolate.h

 // 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.
 
 #ifndef VM_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include <limits.h>
 
 #include "include/dart_api.h"
@@ skipping 57 matching lines @@
   intptr_t active_ports() const { return active_ports_; }
   void increment_active_ports() {
     ASSERT(this == Isolate::Current());
     active_ports_++;
   }
   void decrement_active_ports() {
     ASSERT(this == Isolate::Current());
     active_ports_--;
   }
 
+  Dart_Port main_port() { return main_port_; }
+  void set_main_port(Dart_Port port) {
+    ASSERT(main_port_ == 0);  // Only set main port once.
+    main_port_ = port;
+  }
+
   Heap* heap() const { return heap_; }
   void set_heap(Heap* value) { heap_ = value; }
   static intptr_t heap_offset() { return OFFSET_OF(Isolate, heap_); }
 
   ObjectStore* object_store() const { return object_store_; }
   void set_object_store(ObjectStore* value) { object_store_ = value; }
   static intptr_t object_store_offset() {
     return OFFSET_OF(Isolate, object_store_);
   }
 
@@ skipping 146 matching lines @@
 
   static const uword kStackSizeBuffer = (128 * KB);
   static const uword kDefaultStackSize = (1 * MB);
 
   StoreBufferBlock store_buffer_;
   Monitor* monitor_;
   MessageQueue* message_queue_;
   Dart_PostMessageCallback post_message_callback_;
   Dart_ClosePortCallback close_port_callback_;
   intptr_t active_ports_;
+  Dart_Port main_port_;
   Heap* heap_;
   ObjectStore* object_store_;
   StackResource* top_resource_;
   RawContext* top_context_;
   Zone* current_zone_;
 #if defined(DEBUG)
   int32_t no_gc_scope_depth_;
   int32_t no_handle_scope_depth_;
   HandleScope* top_handle_scope_;
 #endif
@@ skipping 22 matching lines @@
 #include "vm/isolate_linux.h"
 #elif defined(TARGET_OS_MACOS)
 #include "vm/isolate_macos.h"
 #elif defined(TARGET_OS_WINDOWS)
 #include "vm/isolate_win.h"
 #else
 #error Unknown target os.
 #endif
 
 #endif  // VM_ISOLATE_H_