Create a VarPrivate interface to contain the scripting helper functions of Var.

ppapi/cpp/var.h

Index: ppapi/cpp/var.h
===================================================================
--- ppapi/cpp/var.h	(revision 80958)
+++ ppapi/cpp/var.h	(working copy)
@@ -60,6 +60,8 @@
 
   Var& operator=(const Var& other);
 
+  // For objects, dictionaries, and arrays, this operator compares object
+  // identity rather than value identity.
   bool operator==(const Var& other) const;
 
   bool is_undefined() const { return var_.type == PP_VARTYPE_UNDEFINED; }
@@ -195,7 +197,7 @@
     PP_Var temp_;
   };
 
- private:
+ protected:
   // Prevent an arbitrary pointer argument from being implicitly converted to
   // a bool at Var construction. If somebody makes such a mistake, (s)he will
   // get a compilation error.