Revert "Hide Isolate pointer from embedder"

runtime/bin/builtin_common.cc

 // Copyright (c) 2015, 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.
 
 #include <stdio.h>
 
 #include "include/dart_api.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/platform.h"
 
 namespace dart {
 namespace bin {
 
 void Builtin::SetLoadPort(Dart_Port port) {
   load_port_ = port;
-  ASSERT(load_port_ != DART_ILLEGAL_PORT);
+  ASSERT(load_port_ != ILLEGAL_PORT);
   Dart_Handle field_name = DartUtils::NewString("_loadPort");
   ASSERT(!Dart_IsError(field_name));
   Dart_Handle builtin_lib =
       Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
   ASSERT(!Dart_IsError(builtin_lib));
   Dart_Handle send_port = Dart_GetField(builtin_lib, field_name);
   ASSERT(!Dart_IsError(send_port));
   if (!Dart_IsNull(send_port)) {
     // Already created and set.
     return;
   }
   send_port = Dart_NewSendPort(load_port_);
   ASSERT(!Dart_IsError(send_port));
   Dart_Handle result = Dart_SetField(builtin_lib, field_name, send_port);
   ASSERT(!Dart_IsError(result));
 }
 
 }  // namespace bin
 }  // namespace dart