Introduce a Gin class instead of using global functions to control gin

gin/gin.h

+// Copyright 2013 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 GIN_GIN_H_
+#define GIN_GIN_H_
+
+#include "base/basictypes.h"
+
+namespace v8 {
+class Isolate;
+}
+
+namespace gin {
+
+class Gin {
+ public:
+  Gin();
+  ~Gin();
+
+  v8::Isolate* isolate() { return isolate_; }
+
+ private:
+  v8::Isolate* isolate_;
+
+ DISALLOW_COPY_AND_ASSIGN(Gin);
+};
+
+}  // namespace gin
+
+#endif  // GIN_INITIALIZE_H_