[Intl] Calls thisBigIntValue in BigInt toLocaleString

Bug: v8:9109
Change-Id: I5a79192c8168c81d8f35711f8983fb1acb260a10
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1559214
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60731}

src/builtins/builtins-bigint.cc

@@ -127,10 +127,17 @@ BUILTIN(BigIntPrototypeToLocaleString) {
   HandleScope scope(isolate);
 #ifdef V8_INTL_SUPPORT
   if (FLAG_harmony_intl_bigint) {
+    // 1. Let x be ? thisBigIntValue(this value).
+    Handle<BigInt> x;
+    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+        isolate, x,
+        ThisBigIntValue(isolate, args.receiver(),
+                        "BigInt.prototype.toLocaleString"));
+
     RETURN_RESULT_OR_FAILURE(
-        isolate, Intl::NumberToLocaleString(isolate, args.receiver(),
-                                            args.atOrUndefined(isolate, 1),
-                                            args.atOrUndefined(isolate, 2)));
+        isolate,
+        Intl::NumberToLocaleString(isolate, x, args.atOrUndefined(isolate, 1),
+                                   args.atOrUndefined(isolate, 2)));
   }
   // Fallbacks to old toString implemention if flag is off or no
   // V8_INTL_SUPPORT

test/test262/testcfg.py

@@ -60,6 +60,7 @@ FEATURE_FLAGS = {
   'export-star-as-namespace-from-module': '--harmony-namespace-exports',
   'Object.fromEntries': '--harmony-object-from-entries',
   'hashbang': '--harmony-hashbang',
+  'BigInt': '--harmony-intl-bigint',
 }
 
 SKIPPED_FEATURES = set(['class-methods-private',