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

ppapi/thunk/enter.h

Index: ppapi/thunk/enter.h
===================================================================
--- ppapi/thunk/enter.h	(revision 87436)
+++ ppapi/thunk/enter.h	(working copy)
@@ -52,11 +52,9 @@
   bool succeeded() const { return !!functions_; }
   bool failed() const { return !functions_; }
 
-  PP_Instance instance() const { return instance_; }
   FunctionsT* functions() { return functions_; }
 
  private:
-  PP_Instance instance_;
   FunctionsT* functions_;
 
   DISALLOW_COPY_AND_ASSIGN(EnterFunction);
@@ -73,20 +71,6 @@
   }
 };
 
-// Used when a caller has a resource, and wants to do EnterFunction for the
-// instance corresponding to that resource.
-template<typename FunctionsT>
-class EnterFunctionGivenResource : public EnterFunction<FunctionsT> {
- public:
-  EnterFunctionGivenResource(PP_Resource resource, bool report_error)
-      : EnterFunction<FunctionsT>(
-            TrackerBase::Get()->GetInstanceForResource(resource),
-            report_error) {
-  }
-};
-
-// EnterResource ---------------------------------------------------------------
-
 template<typename ResourceT>
 class EnterResource {
  public: