Revert of Rename String.prototype.contains to 'includes'.

test/js-perf-test/Strings/harmony-string.js

 // Copyright 2014 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.
 
 new BenchmarkSuite('StringFunctions', [1000], [
   new Benchmark('StringRepeat', false, false, 0,
                 Repeat, RepeatSetup, RepeatTearDown),
   new Benchmark('StringStartsWith', false, false, 0,
                 StartsWith, WithSetup, WithTearDown),
   new Benchmark('StringEndsWith', false, false, 0,
                 EndsWith, WithSetup, WithTearDown),
-  new Benchmark('StringIncludes', false, false, 0,
-                Includes, IncludesSetup, WithTearDown),
+  new Benchmark('StringContains', false, false, 0,
+                Contains, ContainsSetup, WithTearDown),
   new Benchmark('StringFromCodePoint', false, false, 0,
                 FromCodePoint, FromCodePointSetup, FromCodePointTearDown),
   new Benchmark('StringCodePointAt', false, false, 0,
                 CodePointAt, CodePointAtSetup, CodePointAtTearDown),
 ]);
 
 
 var result;
 
 var stringRepeatSource = "abc";
@@ skipping 29 matching lines @@
 }
 
 function StartsWith() {
   result = str.startsWith(substr);
 }
 
 function EndsWith() {
   result = str.endsWith(substr);
 }
 
-function IncludesSetup() {
+function ContainsSetup() {
   str = "def".repeat(100) + "abc".repeat(100) + "qqq".repeat(100);
   substr = "abc".repeat(100);
 }
 
-function Includes() {
-  result = str.includes(substr);
+function Contains() {
+  result = str.contains(substr);
 }
 
 var MAX_CODE_POINT = 0xFFFFF;
 
 function FromCodePointSetup() {
   result = new Array(MAX_CODE_POINT + 1);
 }
 
 function FromCodePoint() {
   for (var i = 0; i <= MAX_CODE_POINT; i++) {
@@ skipping 22 matching lines @@
 function CodePointAt() {
   result = 0;
   for (var i = 0; i <= MAX_CODE_POINT; i++) {
     result += allCodePoints.codePointAt(i);
   }
 }
 
 function CodePointAtTearDown() {
   return result === MAX_CODE_POINT * (MAX_CODE_POINT + 1) / 2;
 }