Rework CallApi*Stubs.

src/s390/interface-descriptors-s390.cc

Index: src/s390/interface-descriptors-s390.cc
diff --git a/src/s390/interface-descriptors-s390.cc b/src/s390/interface-descriptors-s390.cc
index 600d521b04c02dadf68ef5d37d5f05fbb0c31bbe..5c6dda055617b6033e1e93db14d06d4f818ccbfd 100644
--- a/src/s390/interface-descriptors-s390.cc
+++ b/src/s390/interface-descriptors-s390.cc
@@ -334,19 +334,7 @@ void ArgumentAdaptorDescriptor::InitializePlatformSpecific(
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
-void ApiFunctionDescriptor::InitializePlatformSpecific(
-    CallInterfaceDescriptorData* data) {
-  Register registers[] = {
-      r2,  // callee
-      r6,  // call_data
-      r4,  // holder
-      r3,  // api_function_address
-      r5,  // actual number of arguments
-  };
-  data->InitializePlatformSpecific(arraysize(registers), registers);
-}
-
-void ApiAccessorDescriptor::InitializePlatformSpecific(
+void ApiCallbackDescriptorBase::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {
       r2,  // callee