[turbofan] Introduce a Function type and optimize based on it.

src/code-factory.cc

Index: src/code-factory.cc
diff --git a/src/code-factory.cc b/src/code-factory.cc
index e168b9d20cbe082d21fa482239c8a6d7da752dee..44fa32b394bbcea518f72c0157856fbd4240999d 100644
--- a/src/code-factory.cc
+++ b/src/code-factory.cc
@@ -299,6 +299,13 @@ Callable CodeFactory::Call(Isolate* isolate) {
 
 
 // static
+Callable CodeFactory::CallFunction(Isolate* isolate) {
+  return Callable(isolate->builtins()->CallFunction(),
+                  CallTrampolineDescriptor(isolate));
+}
+
+
+// static
 Callable CodeFactory::InterpreterPushArgsAndCall(Isolate* isolate) {
   return Callable(isolate->builtins()->InterpreterPushArgsAndCall(),
                   InterpreterPushArgsAndCallDescriptor(isolate));