Clean up singleton implementation

Move the singleton instances into their namespaces, and use
get()/getInstance() for uniform accesses.

Review-Url: https://codereview.chromium.org/2154843002
diff --git a/fpdfsdk/javascript/global.h b/fpdfsdk/javascript/global.h
index eca9aa1..6604d9b 100644
--- a/fpdfsdk/javascript/global.h
+++ b/fpdfsdk/javascript/global.h
@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "fpdfsdk/javascript/JS_Define.h"
+#include "fpdfsdk/javascript/JS_KeyValue.h"
 
 class CJS_GlobalData;
 class CJS_GlobalVariableArray;
@@ -20,7 +21,7 @@
   JSGlobalData();
   ~JSGlobalData();
 
-  int nType;  // 0:int 1:bool 2:string 3:obj
+  JS_GlobalDataType nType;
   double dData;
   bool bData;
   CFX_ByteString sData;
@@ -53,7 +54,7 @@
   void CommitGlobalPersisitentVariables(IJS_Context* cc);
   void DestroyGlobalPersisitentVariables();
   FX_BOOL SetGlobalVariables(const CFX_ByteString& propname,
-                             int nType,
+                             JS_GlobalDataType nType,
                              double dData,
                              bool bData,
                              const CFX_ByteString& sData,