Make FastNewFunctionContextStub take slots parameter

src/arm64/interface-descriptors-arm64.cc

Index: src/arm64/interface-descriptors-arm64.cc
diff --git a/src/arm64/interface-descriptors-arm64.cc b/src/arm64/interface-descriptors-arm64.cc
index e08d7e2c54b061efa06ec8d96bd66d6fb67463df..787edf2017c8a0a194257c97455d6972f2be0c08 100644
--- a/src/arm64/interface-descriptors-arm64.cc
+++ b/src/arm64/interface-descriptors-arm64.cc
@@ -22,6 +22,11 @@ void CallInterfaceDescriptor::DefaultInitializePlatformSpecific(
                                    default_stub_registers);
 }
 
+const Register FastNewFunctionContextDescriptor::FunctionRegister() {
+  return x1;
+}
+const Register FastNewFunctionContextDescriptor::SlotsRegister() { return x0; }
+
 const Register LoadDescriptor::ReceiverRegister() { return x1; }
 const Register LoadDescriptor::NameRegister() { return x2; }
 const Register LoadDescriptor::SlotRegister() { return x0; }
@@ -72,13 +77,6 @@ void FastNewClosureDescriptor::InitializePlatformSpecific(
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
-void FastNewFunctionContextDescriptor::InitializePlatformSpecific(
-    CallInterfaceDescriptorData* data) {
-  // x1: function
-  Register registers[] = {x1};
-  data->InitializePlatformSpecific(arraysize(registers), registers);
-}
-
 void FastNewObjectDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {x1, x3};