Fix Dartium build: Add missing Dart_ExitIsolate before call to Dart_CreateIsolate.

runtime/vm/dart_api_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 "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "vm/class_finalizer.h"
@@ skipping 1268 matching lines @@
   OS::SNPrint(chars, len, "%s$%s", script_uri, main);
   return chars;
 }
 
 
 DART_EXPORT Dart_Isolate Dart_CreateIsolate(const char* script_uri,
                                             const char* main,
                                             const uint8_t* snapshot,
                                             void* callback_data,
                                             char** error) {
-  TRACE_API_CALL(CURRENT_FUNC);
+  CHECK_NO_ISOLATE(Isolate::Current());
   char* isolate_name = BuildIsolateName(script_uri, main);
   Isolate* isolate = Dart::CreateIsolate(isolate_name);
   free(isolate_name);
   {
     StackZone zone(isolate);
     HANDLESCOPE(isolate);
     const Error& error_obj =
         Error::Handle(isolate,
                       Dart::InitializeIsolate(snapshot, callback_data));
     if (error_obj.IsNull()) {
@@ skipping 4237 matching lines @@
 
 
 DART_EXPORT void Dart_RegisterRootServiceRequestCallback(
     const char* name,
     Dart_ServiceRequestCallback callback,
     void* user_data) {
   Service::RegisterRootEmbedderCallback(name, callback, user_data);
 }
 
 }  // namespace dart