Rename Instance_Trusted to Instance_Private, wire it up in Chrome.

ppapi/cpp/private/var_private.h

Index: ppapi/cpp/private/var_private.h
diff --git a/ppapi/cpp/private/var_private.h b/ppapi/cpp/private/var_private.h
index 55068bc45557504fe35da974e4c9a93b04603c6d..5ab1e07b265a89ab515b7a23d7a8aadac6332ddd 100644
--- a/ppapi/cpp/private/var_private.h
+++ b/ppapi/cpp/private/var_private.h
@@ -9,6 +9,8 @@
 
 namespace pp {
 
+class InstancePrivate;
+
 // VarPrivate is a version of Var that exposes the private scripting API.
 // It's designed to be mostly interchangable with Var since most callers will
 // be dealing with Vars from various places.
@@ -23,7 +25,7 @@ class VarPrivate : public Var {
   VarPrivate(const std::string& utf8_str) : Var(utf8_str) {}
   VarPrivate(PassRef, PP_Var var) : Var(PassRef(), var) {}
   VarPrivate(DontManage, PP_Var var) : Var(DontManage(), var) {}
-  VarPrivate(Instance* instance, deprecated::ScriptableObject* object);
+  VarPrivate(InstancePrivate* instance, deprecated::ScriptableObject* object);
   VarPrivate(const Var& other) : Var(other) {}
 
   virtual ~VarPrivate() {}