Dart: Better handle leak checks. close() is async.

mojo/dart/embedder/isolate_data.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_DART_EMBEDDER_ISOLATE_DATA_H_
 #define MOJO_DART_EMBEDDER_ISOLATE_DATA_H_
 
-#include <stdlib.h>
-#include <string.h>
+#include <set>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "dart/runtime/include/dart_api.h"
 
 namespace mojo {
 namespace dart {
 
 struct IsolateCallbacks {
   base::Callback<Dart_Isolate(const char*,const char*,const char*,void*,char**)>
@@ skipping 16 matching lines @@
         script(script),
         script_uri(script_uri),
         package_root(package_root) {}
 
   void* app;
   bool strict_compilation;
   IsolateCallbacks callbacks;
   std::string script;
   std::string script_uri;
   std::string package_root;
+  std::set<int64_t> unclosed_handles;
 
   DISALLOW_COPY_AND_ASSIGN(IsolateData);
 };
 
 }  // namespace dart
 }  // namespace mojo
 
 #endif  // MOJO_DART_EMBEDDER_ISOLATE_DATA_H_