Fix leaks related to the usage of JSE runtime data

fxjs/cfxjse_runtimedata.h

 // Copyright 2016 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef FXJS_CFXJSE_RUNTIMEDATA_H_
 #define FXJS_CFXJSE_RUNTIMEDATA_H_
 
+#include <memory>
+
 #include "v8/include/v8.h"
 
 class CFXJSE_RuntimeList;
 
 class CFXJSE_RuntimeData {
  public:
   ~CFXJSE_RuntimeData();
 
   static CFXJSE_RuntimeData* Get(v8::Isolate* pIsolate);
 
   v8::Isolate* m_pIsolate;
   v8::Global<v8::FunctionTemplate> m_hRootContextGlobalTemplate;
   v8::Global<v8::Context> m_hRootContext;
 
  protected:
   explicit CFXJSE_RuntimeData(v8::Isolate* pIsolate);
 
-  static CFXJSE_RuntimeData* Create(v8::Isolate* pIsolate);
+  static std::unique_ptr<CFXJSE_RuntimeData> Create(v8::Isolate* pIsolate);
 
  private:
   CFXJSE_RuntimeData(const CFXJSE_RuntimeData&) = delete;
   CFXJSE_RuntimeData& operator=(const CFXJSE_RuntimeData&) = delete;
 };
 
 #endif  // FXJS_CFXJSE_RUNTIMEDATA_H_