Make FastNewFunctionContextStub take slots parameter

src/full-codegen/x64/full-codegen-x64.cc

Index: src/full-codegen/x64/full-codegen-x64.cc
diff --git a/src/full-codegen/x64/full-codegen-x64.cc b/src/full-codegen/x64/full-codegen-x64.cc
index 9862b805e13bb48f299125dd12d9c223533204ff..67c8ecb908ccd3d4b50c67e9b4581889f4489b00 100644
--- a/src/full-codegen/x64/full-codegen-x64.cc
+++ b/src/full-codegen/x64/full-codegen-x64.cc
@@ -174,15 +174,11 @@ void FullCodeGenerator::Generate() {
       if (info->scope()->new_target_var() != nullptr) {
         __ Push(rdx);  // Preserve new target.
       }
-      if (slots <= FastNewFunctionContextStub::kMaximumSlots) {
-        FastNewFunctionContextStub stub(isolate(), slots);
-        __ CallStub(&stub);
-        // Result of FastNewFunctionContextStub is always in new space.
-        need_write_barrier = false;
-      } else {
-        __ Push(rdi);
-        __ CallRuntime(Runtime::kNewFunctionContext);
-      }
+      FastNewFunctionContextStub stub(isolate());
+      __ Set(FastNewFunctionContextDescriptor::SlotsRegister(), slots);
+      __ CallStub(&stub);
+      // Result of FastNewFunctionContextStub is always in new space.
+      need_write_barrier = false;
       if (info->scope()->new_target_var() != nullptr) {
         __ Pop(rdx);  // Restore new target.
       }