[inspector] Build inspector under v8_enable_inspector build flag.

src/inspector/StringUtil.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_STRINGUTIL_H_
 #define V8_INSPECTOR_STRINGUTIL_H_
 
 #include "src/inspector/Allocator.h"
 #include "src/inspector/String16.h"
-#include "src/inspector/public/StringBuffer.h"
-#include "src/inspector/public/StringView.h"
 
-#include <v8.h>
+#include "include/v8-inspector.h"
 
 namespace v8_inspector {
 
 namespace protocol {
 
 class Value;
 
 using String = v8_inspector::String16;
 using StringBuilder = v8_inspector::String16Builder;
 
@@ skipping 40 matching lines @@
 
  private:
   explicit StringBufferImpl(String16&);
   String16 m_owner;
   StringView m_string;
 };
 
 }  //  namespace v8_inspector
 
 #endif  // V8_INSPECTOR_STRINGUTIL_H_