Revert 87415 - Convert more interfaces to the new thunk system. This goes up to and including

ppapi/shared_impl/tracker_base.h

Index: ppapi/shared_impl/tracker_base.h
===================================================================
--- ppapi/shared_impl/tracker_base.h	(revision 87436)
+++ ppapi/shared_impl/tracker_base.h	(working copy)
@@ -40,10 +40,6 @@
   // there isn't one.
   virtual FunctionGroupBase* GetFunctionAPI(PP_Instance inst,
                                             pp::proxy::InterfaceID id) = 0;
-
-  // Returns the instance corresponding to the given resource, or 0 if the
-  // resource is invalid.
-  virtual PP_Instance GetInstanceForResource(PP_Resource resource) = 0;
 };
 
 }  // namespace ppapi