Use Scope::function_kind_ to distinguish arrow function scopes

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index a2138ec2f2a45a90929062a5c189e1dfe3b56378..0e30a9468890cbca262bb992a4e5fddf2bba0fa2 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -757,8 +757,7 @@ enum ScopeType {
   SCRIPT_SCOPE,    // The top-level scope for a script or a top-level eval.
   CATCH_SCOPE,     // The scope introduced by catch.
   BLOCK_SCOPE,     // The scope introduced by a new block.
-  WITH_SCOPE,      // The scope introduced by with.
-  ARROW_SCOPE      // The top-level scope for an arrow function literal.
+  WITH_SCOPE       // The scope introduced by with.
 };
 
 // The mips architecture prior to revision 5 has inverted encoding for sNaN.