Make FastNewFunctionContextStub take slots parameter

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index 650c83a2ad05a9fa72ad94d98e878b7367b352c6..430090c2473e5a41acc72bae2014da579e14c9cc 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -473,8 +473,12 @@ class FastNewClosureDescriptor : public CallInterfaceDescriptor {
 
 class FastNewFunctionContextDescriptor : public CallInterfaceDescriptor {
  public:
-  DEFINE_PARAMETERS(kFunction)
-  DECLARE_DESCRIPTOR(FastNewFunctionContextDescriptor, CallInterfaceDescriptor)
+  DEFINE_PARAMETERS(kFunction, kSlots)
+  DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(FastNewFunctionContextDescriptor,
+                                               CallInterfaceDescriptor)
+
+  static const Register FunctionRegister();
+  static const Register SlotsRegister();
 };
 
 class FastNewObjectDescriptor : public CallInterfaceDescriptor {