Add ES2015 RegExp full subclassing semantics behind a flag

src/js/prologue.js

 // Copyright 2015 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, extrasUtils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 108 matching lines @@
   SetFunctionName(getter, name, "get");
   SetFunctionName(setter, name, "set");
   %FunctionRemovePrototype(getter);
   %FunctionRemovePrototype(setter);
   %DefineAccessorPropertyUnchecked(object, name, getter, setter, DONT_ENUM);
   %SetNativeFlag(getter);
   %SetNativeFlag(setter);
 }
 
 
+function OverrideFunction(object, name, f, afterInitialBootstrap) {
+  %CheckIsBootstrapping();
+  %ObjectDefineProperty(object, name, { value: f,
+                                        writeable: true,
+                                        configurable: true,
+                                        enumerable: false });
+  SetFunctionName(f, name);
+  if (!afterInitialBootstrap) %FunctionRemovePrototype(f);
+  %SetNativeFlag(f);
+}
+
+
 // Prevents changes to the prototype of a built-in function.
 // The "prototype" property of the function object is made non-configurable,
 // and the prototype object is made non-extensible. The latter prevents
 // changing the __proto__ property.
 function SetUpLockedPrototype(
     constructor, fields, methods) {
   %CheckIsBootstrapping();
   var prototype = constructor.prototype;
   // Install functions first, because this function is used to initialize
   // PropertyDescriptor itself.
@@ skipping 41 matching lines @@
     "MapIterator",
     "MapIteratorNext",
     "MaxSimple",
     "MinSimple",
     "ObjectDefineProperty",
     "ObserveArrayMethods",
     "ObserveObjectMethods",
     "PromiseChain",
     "PromiseDeferred",
     "PromiseResolved",
+    "RegExpSubclassExecJS",
+    "RegExpSubclassMatch",
+    "RegExpSubclassReplace",
+    "RegExpSubclassSearch",
+    "RegExpSubclassSplit",
+    "RegExpSubclassTest",
     "SetIterator",
     "SetIteratorNext",
     "SetValues",
     "SymbolToString",
     "ToPositiveInteger",
     // From runtime:
     "is_concat_spreadable_symbol",
     "iterator_symbol",
     "promise_status_symbol",
     "promise_value_symbol",
     "object_freeze",
     "object_is_frozen",
     "object_is_sealed",
     "reflect_apply",
     "reflect_construct",
     "regexp_flags_symbol",
     "to_string_tag_symbol",
     "object_to_string",
     "species_symbol",
+    "match_symbol",
+    "replace_symbol",
+    "search_symbol",
+    "split_symbol",
   ];
 
   var filtered_exports = {};
   %OptimizeObjectForAddingMultipleProperties(
       filtered_exports, expose_list.length);
   for (var key of expose_list) {
     filtered_exports[key] = exports_container[key];
   }
   %ToFastProperties(filtered_exports);
   exports_container = filtered_exports;
@@ skipping 58 matching lines @@
 
 utils.Import = Import;
 utils.ImportNow = ImportNow;
 utils.Export = Export;
 utils.ImportFromExperimental = ImportFromExperimental;
 utils.SetFunctionName = SetFunctionName;
 utils.InstallConstants = InstallConstants;
 utils.InstallFunctions = InstallFunctions;
 utils.InstallGetter = InstallGetter;
 utils.InstallGetterSetter = InstallGetterSetter;
+utils.OverrideFunction = OverrideFunction;
 utils.SetUpLockedPrototype = SetUpLockedPrototype;
 utils.PostNatives = PostNatives;
 utils.PostExperimentals = PostExperimentals;
 utils.PostDebug = PostDebug;
 
 %ToFastProperties(utils);
 
 // -----------------------------------------------------------------------
 
 %OptimizeObjectForAddingMultipleProperties(extrasUtils, 5);
@@ skipping 33 matching lines @@
 
 extrasUtils.uncurryThis = function uncurryThis(func) {
   return function(thisArg, ...args) {
     return %reflect_apply(func, thisArg, args);
   };
 };
 
 %ToFastProperties(extrasUtils);
 
 })