Clean up singleton implementation

fpdfsdk/javascript/JS_GlobalData.cpp

Index: fpdfsdk/javascript/JS_GlobalData.cpp
diff --git a/fpdfsdk/javascript/JS_GlobalData.cpp b/fpdfsdk/javascript/JS_GlobalData.cpp
index 14c36530d5d65c2d2483596f16de47b514ce8bf8..fb470a02ebf1f74122dc47e963ce5880f08fbf35 100644
--- a/fpdfsdk/javascript/JS_GlobalData.cpp
+++ b/fpdfsdk/javascript/JS_GlobalData.cpp
@@ -100,21 +100,21 @@ static bool TrimPropName(CFX_ByteString* sPropName) {
   return sPropName->GetLength() != 0;
 }
 
-CJS_GlobalData* CJS_GlobalData::g_Instance = nullptr;
+CJS_GlobalData* CJS_GlobalData::m_pInstance = nullptr;
 
 // static
 CJS_GlobalData* CJS_GlobalData::GetRetainedInstance(CPDFDoc_Environment* pApp) {
-  if (!g_Instance) {
-    g_Instance = new CJS_GlobalData();
+  if (!m_pInstance) {
+    m_pInstance = new CJS_GlobalData();
   }
-  ++g_Instance->m_RefCount;
-  return g_Instance;
+  ++m_pInstance->m_RefCount;
+  return m_pInstance;
 }
 
 void CJS_GlobalData::Release() {
   if (!--m_RefCount) {
-    delete g_Instance;
-    g_Instance = nullptr;
+    delete m_pInstance;
+    m_pInstance = nullptr;
   }
 }