[turbofan] Call FastNewContextStub for function context.

src/code-factory.cc

Index: src/code-factory.cc
diff --git a/src/code-factory.cc b/src/code-factory.cc
index 9e776b40fc5ea112ce51bddca2079fdbf2a49d2a..cfa11a7e62371aff04700b5f91f8153efaf5aba8 100644
--- a/src/code-factory.cc
+++ b/src/code-factory.cc
@@ -227,6 +227,13 @@ Callable CodeFactory::FastCloneShallowObject(Isolate* isolate, int length) {
 
 
 // static
+Callable CodeFactory::FastNewContext(Isolate* isolate, int slot_count) {
+  FastNewContextStub stub(isolate, slot_count);
+  return Callable(stub.GetCode(), stub.GetCallInterfaceDescriptor());
+}
+
+
+// static
 Callable CodeFactory::FastNewClosure(Isolate* isolate,
                                      LanguageMode language_mode,
                                      FunctionKind kind) {