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

gin/runner.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_RUNNER_H_
 #define GIN_RUNNER_H_
 
 #include <string>
 
 #include "base/memory/weak_ptr.h"
@@ skipping 32 matching lines @@
   base::WeakPtr<Runner> GetWeakPtr() {
     return weak_factory_.GetWeakPtr();
   }
 
   class Scope {
    public:
     explicit Scope(Runner* runner);
     ~Scope();
 
    private:
+    v8::Isolate::Scope isolate_scope_;
     v8::HandleScope handle_scope_;
     v8::Context::Scope scope_;
 
     DISALLOW_COPY_AND_ASSIGN(Scope);
   };
 
  private:
   friend class Scope;
 
   RunnerDelegate* delegate_;
 
   base::WeakPtrFactory<Runner> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Runner);
 };
 
 }  // namespace gin
 
 #endif  // GIN_RUNNER_H_