Revert "Hide Isolate pointer from embedder"

runtime/bin/vmservice_impl.cc

 // Copyright (c) 2013, 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 "bin/vmservice_impl.h"
 
 #include "include/dart_api.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
@@ skipping 143 matching lines @@
   return NULL;
 }
 
 
 const char* VmService::error_msg_ = NULL;
 char VmService::server_ip_[kServerIpStringBufferSize];
 intptr_t VmService::server_port_ = 0;
 
 bool VmService::Setup(const char* server_ip, intptr_t server_port) {
   Dart_Isolate isolate = Dart_CurrentIsolate();
-  ASSERT(isolate != DART_ILLEGAL_ISOLATE);
+  ASSERT(isolate != NULL);
   SetServerIPAndPort("", 0);
 
   Dart_Handle result;
 
   Dart_Handle builtin_lib =
       Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
   SHUTDOWN_ON_ERROR(builtin_lib);
 
   // Prepare for script loading by setting up the 'print' and 'timer'
   // closures and setting up 'package root' for URI resolution.
@@ skipping 201 matching lines @@
   Dart_Handle source = GetSource(url_string);
   if (Dart_IsError(source)) {
     return source;
   }
   return Dart_LoadSource(library, url, source, 0, 0);
 }
 
 
 }  // namespace bin
 }  // namespace dart