Add ptr_util.h from base until std::make_unique<> available

fpdfsdk/javascript/JS_Runtime_Stub.cpp

 // Copyright 2015 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
 
 #include <memory>
 
 #include "fpdfsdk/javascript/ijs_context.h"
 #include "fpdfsdk/javascript/ijs_runtime.h"
+#include "third_party/base/ptr_util.h"
 
 class CJS_ContextStub final : public IJS_Context {
  public:
   CJS_ContextStub() {}
   ~CJS_ContextStub() override {}
 
   // IJS_Context:
   FX_BOOL RunScript(const CFX_WideString& script,
                     CFX_WideString* info) override {
     return FALSE;
@@ skipping 96 matching lines @@
   void OnExternal_Exec() override {}
 };
 
 class CJS_RuntimeStub final : public IJS_Runtime {
  public:
   CJS_RuntimeStub() : m_pDoc(nullptr) {}
   ~CJS_RuntimeStub() override {}
 
   IJS_Context* NewContext() override {
     if (!m_pContext)
-      m_pContext = WrapUnique(new CJS_ContextStub());
+      m_pContext = pdfium::MakeUnique<CJS_ContextStub>();
     return GetCurrentContext();
   }
 
   IJS_Context* GetCurrentContext() override { return m_pContext.get(); }
   void ReleaseContext(IJS_Context* pContext) override {}
 
   void SetReaderDocument(CPDFSDK_Document* pReaderDoc) override {
     m_pDoc = pReaderDoc;
   }
   CPDFSDK_Document* GetReaderDocument() override { return m_pDoc; }
@@ skipping 21 matching lines @@
 // static
 void IJS_Runtime::Initialize(unsigned int slot, void* isolate) {}
 
 // static
 void IJS_Runtime::Destroy() {}
 
 // static
 IJS_Runtime* IJS_Runtime::Create(CPDFSDK_Environment* pEnv) {
   return new CJS_RuntimeStub;
 }