[es6] do not add caller/arguments to ES6 function definitions

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 3b4b7992c099bbc5f7393fc37d7fa5549284e119..4fe0621e04c5efc4d4234dc509e161cf1fb0d522 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -582,17 +582,16 @@ class Context: public FixedArray {
     }
 
     if (IsConstructor(kind)) {
-      return is_strong(language_mode) ? STRONG_CONSTRUCTOR_MAP_INDEX :
-             is_strict(language_mode) ? STRICT_FUNCTION_MAP_INDEX
-                                      : SLOPPY_FUNCTION_MAP_INDEX;
+      // Use strict function map (no own "caller" / "arguments")
+      return is_strong(language_mode) ? STRONG_CONSTRUCTOR_MAP_INDEX
+                                      : STRICT_FUNCTION_MAP_INDEX;
     }
 
     if (IsArrowFunction(kind) || IsConciseMethod(kind) ||
         IsAccessorFunction(kind)) {
-      return is_strong(language_mode) ? STRONG_FUNCTION_MAP_INDEX :
-             is_strict(language_mode) ?
-                 STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX :
-                 SLOPPY_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX;
+      return is_strong(language_mode)
+                 ? STRONG_FUNCTION_MAP_INDEX
+                 : STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX;
     }
 
     return is_strong(language_mode) ? STRONG_FUNCTION_MAP_INDEX :