Reland of Put RegExp js code in strict mode (patchset #2 id:20001 of https://codereview.chromium.or…

test/mjsunit/regexp-lastIndex.js

+// Copyright 2016 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.
+
+// lastIndex is set only for global or sticky RegExps. On failure to find
+// a match, it is set to 0. If a set fails, then it acts as if in strict mode
+// and throws.
+
+var re = /x/g;
+Object.defineProperty(re, 'lastIndex', {writable: false});
+assertThrows(() => re.exec(""), TypeError);
+assertThrows(() => re.exec("x"), TypeError);
+
+var re = /x/y;
+Object.defineProperty(re, 'lastIndex', {writable: false});
+assertThrows(() => re.exec(""), TypeError);
+assertThrows(() => re.exec("x"), TypeError);
+
+var re = /x/;
+Object.defineProperty(re, 'lastIndex', {writable: false});
+assertEquals(null, re.exec(""));
+assertEquals(["x"], re.exec("x"));