[bindings] Migrate V8TestingScope out of V8Binding.h/cpp

Source/bindings/core/v8/V8TestingScope.h

+// Copyright (c) 2015 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 V8TestingScope_h
+#define V8TestingScope_h
+
+#include "bindings/core/v8/ScriptState.h"
+
+#include <v8.h>
+
+namespace blink {
+
+class V8TestingScope {
+public:
+    explicit V8TestingScope(v8::Isolate*);
+    ScriptState* scriptState() const;
+    v8::Isolate* isolate() const;
+    ~V8TestingScope();
+
+private:
+    v8::HandleScope m_handleScope;
+    v8::Context::Scope m_contextScope;
+    RefPtr<ScriptState> m_scriptState;
+};
+
+} // namespace blink
+
+#endif // V8TestingScope_h