Clean up singleton implementation

fpdfsdk/fpdfxfa/fpdfxfa_app.cpp

 // Copyright 2014 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 "fpdfsdk/fpdfxfa/include/fpdfxfa_app.h"
 
 #include "fpdfsdk/fpdfxfa/include/fpdfxfa_util.h"
 #include "fpdfsdk/include/fsdk_define.h"
 #include "fpdfsdk/include/fsdk_mgr.h"
 #include "xfa/fxbarcode/include/BC_Library.h"
 #include "xfa/fxfa/include/xfa_ffapp.h"
 #include "xfa/fxfa/include/xfa_fontmgr.h"
 
-CPDFXFA_App* CPDFXFA_App::g_pApp = nullptr;
+CPDFXFA_App* CPDFXFA_App::m_pApp = nullptr;
 
 CPDFXFA_App* CPDFXFA_App::GetInstance() {
-  if (!g_pApp) {
-    g_pApp = new CPDFXFA_App();
+  if (!m_pApp) {
+    m_pApp = new CPDFXFA_App();
   }
-  return g_pApp;
+  return m_pApp;
 }
 
 void CPDFXFA_App::ReleaseInstance() {
-  delete g_pApp;
-  g_pApp = nullptr;
+  delete m_pApp;
+  m_pApp = nullptr;
 }
 
 CPDFXFA_App::CPDFXFA_App()
     : m_bJavaScriptInitialized(FALSE),
       m_pXFAApp(nullptr),
       m_pIsolate(nullptr),
       m_csAppType(JS_STR_VIEWERTYPE_STANDARD) {
   m_pEnvList.RemoveAll();
 }
 
@@ skipping 324 matching lines @@
   }
 }
 
 IFWL_AdapterTimerMgr* CPDFXFA_App::GetTimerMgr() {
   CXFA_FWLAdapterTimerMgr* pAdapter = nullptr;
   CPDFDoc_Environment* pEnv = m_pEnvList.GetAt(0);
   if (pEnv)
     pAdapter = new CXFA_FWLAdapterTimerMgr(pEnv);
   return pAdapter;
 }