[destructuring] Support computed property names in patterns.

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 443354fafb8d866ebd83cf3cf15658ed69342578..c948b2d204cc0af421c7f783b7c3c4f642ddfc05 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -2556,8 +2556,10 @@ typename ParserBase<Traits>::ExpressionT ParserBase<Traits>::ParsePropertyName(
       if (allow_harmony_computed_property_names_) {
         *is_computed_name = true;
         Consume(Token::LBRACK);
-        ExpressionT expression =
-            ParseAssignmentExpression(true, classifier, CHECK_OK);
+        ExpressionClassifier computed_name_classifier;
+        ExpressionT expression = ParseAssignmentExpression(
+            true, &computed_name_classifier, CHECK_OK);
+        classifier->AccumulateReclassifyingAsPattern(computed_name_classifier);
         Expect(Token::RBRACK, CHECK_OK);
         return expression;
       }