[parser] Allow duplicate __proto__ keys in patterns

src/parsing/expression-classifier.h

 // 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.
 
 #ifndef V8_PARSING_EXPRESSION_CLASSIFIER_H
 #define V8_PARSING_EXPRESSION_CLASSIFIER_H
 
 #include "src/messages.h"
 #include "src/parsing/scanner.h"
 #include "src/parsing/token.h"
@@ skipping 327 matching lines @@
     invalid_productions_ &= ~CoverInitializedNameProduction;
   }
 
   void ForgiveAssignmentPatternError() {
     if (!(invalid_productions_ & AssignmentPatternProduction)) return;
     Error& e = reported_error(kAssignmentPatternProduction);
     e.kind = kUnusedError;
     invalid_productions_ &= ~AssignmentPatternProduction;
   }
 
+  void ForgiveExpressionError() {
+    if (!(invalid_productions_ & ExpressionProduction)) return;
+    Error& e = reported_error(kExpressionProduction);
+    e.kind = kUnusedError;
+    invalid_productions_ &= ~ExpressionProduction;
+  }
+
   void Accumulate(ExpressionClassifier* inner,
                   unsigned productions = StandardProductions,
                   bool merge_non_patterns = true) {
     DCHECK_EQ(inner->reported_errors_, reported_errors_);
     DCHECK_EQ(inner->reported_errors_begin_, reported_errors_end_);
     DCHECK_EQ(inner->reported_errors_end_, reported_errors_->length());
     if (merge_non_patterns) MergeNonPatterns(inner);
     // Propagate errors from inner, but don't overwrite already recorded
     // errors.
     unsigned non_arrow_inner_invalid_productions =
@@ skipping 136 matching lines @@
 };
 
 
 #undef ERROR_CODES
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_EXPRESSION_CLASSIFIER_H