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

gin/test/v8_test.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_TEST_V8_TEST_H_
 #define GIN_TEST_V8_TEST_H_
 
+#include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "v8/include/v8.h"
 
 namespace gin {
 
+class Gin;
+
 // A base class for tests that use v8.
 class V8Test : public testing::Test {
  public:
   V8Test();
   virtual ~V8Test();
 
   virtual void SetUp() OVERRIDE;
   virtual void TearDown() OVERRIDE;
 
  protected:
-  v8::Isolate* isolate_;
+  scoped_ptr<Gin> instance_;
   v8::Persistent<v8::Context> context_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(V8Test);
 };
 
 }  // namespace gin
 
 #endif  // GIN_TEST_V8_TEST_H_