Clean up singleton implementation

core/fpdfapi/cpdf_modulemgr.cpp

Index: core/fpdfapi/cpdf_modulemgr.cpp
diff --git a/core/fpdfapi/cpdf_modulemgr.cpp b/core/fpdfapi/cpdf_modulemgr.cpp
index fe5368d3f7ca82ce8605324f5ed0107969224f24..e26bb91cafeb934292e6de9690f768fed53da7b4 100644
--- a/core/fpdfapi/cpdf_modulemgr.cpp
+++ b/core/fpdfapi/cpdf_modulemgr.cpp
@@ -9,27 +9,19 @@
 #include "core/fpdfapi/fpdf_page/cpdf_pagemodule.h"
 #include "core/fxcodec/include/fx_codec.h"
 
-namespace {
-
-CPDF_ModuleMgr* g_FPDFAPI_pDefaultMgr = nullptr;
-
-}  // namespace
+CPDF_ModuleMgr* CPDF_ModuleMgr::m_pDefaultMgr = nullptr;
 
 // static
 CPDF_ModuleMgr* CPDF_ModuleMgr::Get() {
-  return g_FPDFAPI_pDefaultMgr;
-}
-
-// static
-void CPDF_ModuleMgr::Create() {
-  ASSERT(!g_FPDFAPI_pDefaultMgr);
-  g_FPDFAPI_pDefaultMgr = new CPDF_ModuleMgr;
+  if (!m_pDefaultMgr)
+    m_pDefaultMgr = new CPDF_ModuleMgr;
+  return m_pDefaultMgr;
 }
 
 // static
 void CPDF_ModuleMgr::Destroy() {
-  delete g_FPDFAPI_pDefaultMgr;
-  g_FPDFAPI_pDefaultMgr = nullptr;
+  delete m_pDefaultMgr;
+  m_pDefaultMgr = nullptr;
 }
 
 CPDF_ModuleMgr::CPDF_ModuleMgr() : m_pCodecModule(nullptr) {}