[inspector] Build inspector under v8_enable_inspector build flag.

src/inspector/public/StringBuffer.h

-// Copyright 2016 the V8 project 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 V8_INSPECTOR_PUBLIC_STRINGBUFFER_H_
-#define V8_INSPECTOR_PUBLIC_STRINGBUFFER_H_
-
-#include "src/inspector/public/StringView.h"
-
-#include <memory>
-
-namespace v8_inspector {
-
-class PLATFORM_EXPORT StringBuffer {
- public:
-  virtual ~StringBuffer() {}
-  virtual const StringView& string() = 0;
-  // This method copies contents.
-  static std::unique_ptr<StringBuffer> create(const StringView&);
-};
-
-}  // namespace v8_inspector
-
-#endif  // V8_INSPECTOR_PUBLIC_STRINGBUFFER_H_