[compiler] Introduce code stubs for string relational comparisons.

src/code-factory.h

Index: src/code-factory.h
diff --git a/src/code-factory.h b/src/code-factory.h
index 6431534872152ffeb3402de7af3380e6a26928e2..7c7c28d1518eae613219dba1c61c5e6d7be953f7 100644
--- a/src/code-factory.h
+++ b/src/code-factory.h
@@ -87,6 +87,10 @@ class CodeFactory final {
   static Callable StringCompare(Isolate* isolate);
   static Callable StringEqual(Isolate* isolate);
   static Callable StringNotEqual(Isolate* isolate);
+  static Callable StringLessThan(Isolate* isolate);
+  static Callable StringLessThanOrEqual(Isolate* isolate);
+  static Callable StringGreaterThan(Isolate* isolate);
+  static Callable StringGreaterThanOrEqual(Isolate* isolate);
   static Callable SubString(Isolate* isolate);
 
   static Callable Typeof(Isolate* isolate);