[builtins] Remove BigIntConstructor_ConstructStub builtin

This brings us closer to our goal of deprecating the `construct_stub`
field in `SharedFunctionInfo`.

Bug: v8:7503
Change-Id: I215539fb8ac52fd437d3c04a02ecba2cd38cd101
Reviewed-on: https://chromium-review.googlesource.com/940125Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51627}

src/bootstrapper.cc

@@ -4369,7 +4369,7 @@ void Genesis::InitializeGlobal_harmony_bigint() {
   bigint_fun->shared()->set_builtin_function_id(kBigIntConstructor);
   bigint_fun->shared()->DontAdaptArguments();
   bigint_fun->shared()->SetConstructStub(
-      *BUILTIN_CODE(isolate(), BigIntConstructor_ConstructStub));
+      *BUILTIN_CODE(isolate(), JSBuiltinsConstructStub));
   bigint_fun->shared()->set_length(1);
   InstallWithIntrinsicDefaultProto(isolate(), bigint_fun,
                                    Context::BIGINT_FUNCTION_INDEX);

src/builtins/builtins-bigint.cc

@@ -13,6 +13,7 @@ namespace internal {
 
 BUILTIN(BigIntConstructor) {
   HandleScope scope(isolate);
+  if (args.new_target()->IsUndefined(isolate)) {  // [[Call]]
     Handle<Object> value = args.atOrUndefined(isolate, 1);
 
     if (value->IsJSReceiver()) {
@@ -27,13 +28,11 @@ BUILTIN(BigIntConstructor) {
     } else {
       RETURN_RESULT_OR_FAILURE(isolate, BigInt::FromObject(isolate, value));
     }
-}
-
-BUILTIN(BigIntConstructor_ConstructStub) {
-  HandleScope scope(isolate);
+  } else {  // [[Construct]]
     THROW_NEW_ERROR_RETURN_FAILURE(
         isolate, NewTypeError(MessageTemplate::kNotConstructor,
                               isolate->factory()->BigInt_string()));
+  }
 }
 
 BUILTIN(BigIntAsUintN) {

src/builtins/builtins-definitions.h

@@ -374,7 +374,6 @@ namespace internal {
                                                                                \
   /* BigInt */                                                                 \
   CPP(BigIntConstructor)                                                       \
-  CPP(BigIntConstructor_ConstructStub)                                         \
   CPP(BigIntAsUintN)                                                           \
   CPP(BigIntAsIntN)                                                            \
   CPP(BigIntPrototypeToLocaleString)                                           \