Support the o?.#foo syntax

Bug: v8:10371, v8:10396
Change-Id: I55359ac5d96369962d472f8a7e5d01303b823be0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2145240
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67108}

src/parsing/parser-base.h

@@ -3397,13 +3397,7 @@ ParserBase<Impl>::ParseLeftHandSideContinuation(ExpressionT result) {
         if (is_optional) {
           DCHECK_EQ(scanner()->current_token(), Token::QUESTION_PERIOD);
           int pos = position();
-          Token::Value next = Next();
-          if (V8_UNLIKELY(!Token::IsPropertyName(next))) {
-            ReportUnexpectedToken(next);
-            return impl()->FailureExpression();
-          }
-          IdentifierT name = impl()->GetSymbol();
-          ExpressionT key = factory()->NewStringLiteral(name, position());
+          ExpressionT key = ParsePropertyOrPrivatePropertyName();
           result = factory()->NewProperty(result, key, pos, is_optional);
           break;
         }

test/mjsunit/harmony/optional-chaining.js

@@ -101,7 +101,6 @@ shouldThrowSyntaxError('function foo() { new?.target; }');
 
 shouldThrowSyntaxError('function tag() {} tag?.``;');
 shouldThrowSyntaxError('const o = { tag() {} }; o?.tag``;');
-shouldThrowSyntaxError('class A { #foo = "hi"; constructor() { this?.#foo; } }')
 
 const o2 = {
   count: 0,

test/test262/test262.status

@@ -702,10 +702,6 @@
   'language/expressions/logical-assignment/lgcl-or-assignment-operator-unresolved-rhs-put': [FAIL],
   'language/expressions/logical-assignment/lgcl-or-whitespace': [FAIL],
 
-  # https://bugs.chromium.org/p/v8/issues/detail?id=10396
-  'language/expressions/class/elements/grammar-private-field-optional-chaining': [FAIL],
-  'language/statements/class/elements/grammar-private-field-optional-chaining': [FAIL],
-
   # https://bugs.chromium.org/p/v8/issues/detail?id=10397
   'language/statements/for-await-of/iterator-close-throw-get-method-abrupt': [FAIL],
   'language/statements/for-of/iterator-close-throw-get-method-abrupt': [FAIL],