Revert of [stubs] Port String.prototype.substring to TurboFan

src/js/string.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
@@ skipping 219 matching lines @@
   if (IS_UNDEFINED(separator)) return [subject];
 
   var separator_length = separator_string.length;
 
   // If the separator string is empty then return the elements in the subject.
   if (separator_length === 0) return %StringToArray(subject, limit);
 
   return %StringSplit(subject, separator_string, limit);
 }
 
+
+// ECMA-262 section 15.5.4.15
+function StringSubstring(start, end) {
+  CHECK_OBJECT_COERCIBLE(this, "String.prototype.subString");
+
+  var s = TO_STRING(this);
+  var s_len = s.length;
+
+  var start_i = TO_INTEGER(start);
+  if (start_i < 0) {
+    start_i = 0;
+  } else if (start_i > s_len) {
+    start_i = s_len;
+  }
+
+  var end_i = s_len;
+  if (!IS_UNDEFINED(end)) {
+    end_i = TO_INTEGER(end);
+    if (end_i > s_len) {
+      end_i = s_len;
+    } else {
+      if (end_i < 0) end_i = 0;
+      if (start_i > end_i) {
+        var tmp = end_i;
+        end_i = start_i;
+        start_i = tmp;
+      }
+    }
+  }
+
+  return %_SubString(s, start_i, end_i);
+}
+
+
 // ecma262/#sec-string.prototype.substr
 function StringSubstr(start, length) {
   CHECK_OBJECT_COERCIBLE(this, "String.prototype.substr");
   var s = TO_STRING(this);
   var size = s.length;
   start = TO_INTEGER(start);
   length = IS_UNDEFINED(length) ? size : TO_INTEGER(length);
 
   if (start < 0) start = MaxSimple(size + start, 0);
   length = MinSimple(MaxSimple(length, 0), size - start);
@@ skipping 300 matching lines @@
   "concat", StringConcat,
   "endsWith", StringEndsWith,
   "includes", StringIncludes,
   "indexOf", StringIndexOf,
   "match", StringMatchJS,
   "repeat", StringRepeat,
   "replace", StringReplace,
   "search", StringSearch,
   "slice", StringSlice,
   "split", StringSplitJS,
+  "substring", StringSubstring,
   "substr", StringSubstr,
   "startsWith", StringStartsWith,
   "toLowerCase", StringToLowerCaseJS,
   "toLocaleLowerCase", StringToLocaleLowerCase,
   "toUpperCase", StringToUpperCaseJS,
   "toLocaleUpperCase", StringToLocaleUpperCase,
 
   "link", StringLink,
   "anchor", StringAnchor,
   "fontcolor", StringFontcolor,
@@ skipping 12 matching lines @@
 // -------------------------------------------------------------------
 // Exports
 
 utils.Export(function(to) {
   to.StringIndexOf = StringIndexOf;
   to.StringMatch = StringMatchJS;
   to.StringReplace = StringReplace;
   to.StringSlice = StringSlice;
   to.StringSplit = StringSplitJS;
   to.StringSubstr = StringSubstr;
+  to.StringSubstring = StringSubstring;
 });
 
 })