[intl] Use null prototypes rather than object prototypes

The use of object literals comes with Object.prototype as the
prototype. Some of these were required by the specification, but
a change to the specification is proposed in
https://github.com/tc39/ecma402/pull/170 to eliminate this.
Some of them are unobservable, since Object.prototype is always
shadowed, and defineProperty is used rather than ordinary set.
However, just to be cautious, all object literals in
intl.js except the ones that need it (namely the result of
resolvedOptions()) are changed to a null prototype

Tests are in the test262 PR https://github.com/tc39/test262/pull/1220

Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I1f684615e60b523441baf31350d752585d8f96d1
Reviewed-on: https://chromium-review.googlesource.com/657839Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Daniel Ehrenberg <littledan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48505}

src/js/intl.js

@@ -272,7 +272,7 @@ function supportedLocalesOf(service, locales, options) {
 
   // Provide defaults if matcher was not specified.
   if (IS_UNDEFINED(options)) {
-    options = {};
+    options = {__proto__: null};
   } else {
     options = TO_OBJECT(options);
   }
@@ -483,12 +483,12 @@ function parseExtension(extension) {
   // Assume ['', 'u', ...] input, but don't throw.
   if (extensionSplit.length <= 2 ||
       (extensionSplit[0] !== '' && extensionSplit[1] !== 'u')) {
-    return {};
+    return {__proto__: null};
   }
 
   // Key is {2}alphanum, value is {3,8}alphanum.
   // Some keys may not have explicit values (booleans).
-  var extensionMap = {};
+  var extensionMap = {__proto__: null};
   var key = UNDEFINED;
   var value = UNDEFINED;
   for (var i = 2; i < extensionSplit.length; ++i) {
@@ -510,7 +510,7 @@ function parseExtension(extension) {
       }
     } else {
       // There is a value that's too long, or that doesn't have a key.
-      return {};
+      return {__proto__: null};
     }
   }
   if (!IS_UNDEFINED(key) && !(key in extensionMap)) {
@@ -915,12 +915,12 @@ DEFINE_METHOD(
  */
 function CreateCollator(locales, options) {
   if (IS_UNDEFINED(options)) {
-    options = {};
+    options = {__proto__: null};
   }
 
   var getOption = getGetOption(options, 'collator');
 
-  var internalOptions = {};
+  var internalOptions = {__proto__: null};
 
   defineWEProperty(internalOptions, 'usage', getOption(
     'usage', 'string', ['sort', 'search'], 'sort'));
@@ -988,7 +988,7 @@ function CreateCollator(locales, options) {
   // problems. If malicious user decides to redefine Object.prototype.locale
   // we can't just use plain x.locale = 'us' or in C++ Set("locale", "us").
   // %object_define_properties will either succeed defining or throw an error.
-  var resolved = %object_define_properties({}, {
+  var resolved = %object_define_properties({__proto__: null}, {
     caseFirst: {writable: true},
     collation: {value: internalOptions.collation, writable: true},
     ignorePunctuation: {writable: true},
@@ -1083,21 +1083,21 @@ function PluralRulesConstructor() {
   var options = arguments[1];
 
   if (IS_UNDEFINED(options)) {
-    options = {};
+    options = {__proto__: null};
   }
 
   var getOption = getGetOption(options, 'pluralrules');
 
   var locale = resolveLocale('pluralrules', locales, options);
 
-  var internalOptions = {};
+  var internalOptions = {__proto__: null};
   defineWEProperty(internalOptions, 'type', getOption(
     'type', 'string', ['cardinal', 'ordinal'], 'cardinal'));
 
   SetNumberFormatDigitOptions(internalOptions, options, 0, 3);
 
   var requestedLocale = locale.locale;
-  var resolved = %object_define_properties({}, {
+  var resolved = %object_define_properties({__proto__: null}, {
     type: {value: internalOptions.type, writable: true},
     locale: {writable: true},
     maximumFractionDigits: {writable: true},
@@ -1244,14 +1244,14 @@ function SetNumberFormatDigitOptions(internalOptions, options,
  */
 function CreateNumberFormat(locales, options) {
   if (IS_UNDEFINED(options)) {
-    options = {};
+    options = {__proto__: null};
   }
 
   var getOption = getGetOption(options, 'numberformat');
 
   var locale = resolveLocale('numberformat', locales, options);
 
-  var internalOptions = {};
+  var internalOptions = {__proto__: null};
   defineWEProperty(internalOptions, 'style', getOption(
     'style', 'string', ['decimal', 'percent', 'currency'], 'decimal'));
 
@@ -1301,7 +1301,7 @@ function CreateNumberFormat(locales, options) {
                              getOption, internalOptions);
 
   var requestedLocale = locale.locale + extension;
-  var resolved = %object_define_properties({}, {
+  var resolved = %object_define_properties({__proto__: null}, {
     currency: {writable: true},
     currencyDisplay: {writable: true},
     locale: {writable: true},
@@ -1486,7 +1486,7 @@ function fromLDMLString(ldmlString) {
   // First remove '' quoted text, so we lose 'Uhr' strings.
   ldmlString = %RegExpInternalReplace(GetQuotedStringRE(), ldmlString, '');
 
-  var options = {};
+  var options = {__proto__: null};
   var match = %regexp_internal_match(/E{3,5}/, ldmlString);
   options = appendToDateTimeObject(
       options, 'weekday', match, {EEEEE: 'narrow', EEE: 'short', EEEE: 'long'});
@@ -1562,7 +1562,7 @@ function appendToDateTimeObject(options, option, match, pairs) {
  */
 function toDateTimeOptions(options, required, defaults) {
   if (IS_UNDEFINED(options)) {
-    options = {};
+    options = {__proto__: null};
   } else {
     options = TO_OBJECT(options);
   }
@@ -1622,7 +1622,7 @@ function toDateTimeOptions(options, required, defaults) {
  */
 function CreateDateTimeFormat(locales, options) {
   if (IS_UNDEFINED(options)) {
-    options = {};
+    options = {__proto__: null};
   }
 
   var locale = resolveLocale('dateformat', locales, options);
@@ -1646,7 +1646,7 @@ function CreateDateTimeFormat(locales, options) {
 
   // ICU prefers options to be passed using -u- extension key/values, so
   // we need to build that.
-  var internalOptions = {};
+  var internalOptions = {__proto__: null};
   var extensionMap = parseExtension(locale.extension);
 
   /**
@@ -1662,7 +1662,7 @@ function CreateDateTimeFormat(locales, options) {
                              getOption, internalOptions);
 
   var requestedLocale = locale.locale + extension;
-  var resolved = %object_define_properties({}, {
+  var resolved = %object_define_properties({__proto__: null}, {
     calendar: {writable: true},
     day: {writable: true},
     era: {writable: true},
@@ -1869,18 +1869,18 @@ function canonicalizeTimeZoneID(tzID) {
  */
 function CreateBreakIterator(locales, options) {
   if (IS_UNDEFINED(options)) {
-    options = {};
+    options = {__proto__: null};
   }
 
   var getOption = getGetOption(options, 'breakiterator');
 
-  var internalOptions = {};
+  var internalOptions = {__proto__: null};
 
   defineWEProperty(internalOptions, 'type', getOption(
     'type', 'string', ['character', 'word', 'sentence', 'line'], 'word'));
 
   var locale = resolveLocale('breakiterator', locales, options);
-  var resolved = %object_define_properties({}, {
+  var resolved = %object_define_properties({__proto__: null}, {
     requestedLocale: {value: locale.locale, writable: true},
     type: {value: internalOptions.type, writable: true},
     locale: {writable: true}
@@ -2093,7 +2093,6 @@ DEFINE_METHOD(
   }
 );
 
-var StringPrototypeMethods = {};
 DEFINE_METHODS_LEN(
   GlobalString.prototype,
   {