Only count legacy parser usage if legacy parser had effect.

src/dateparser-inl.h

 // Copyright 2011 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_DATEPARSER_INL_H_
 #define V8_DATEPARSER_INL_H_
 
 #include "src/char-predicates-inl.h"
 #include "src/dateparser.h"
 #include "src/unicode-cache-inl.h"
@@ skipping 57 matching lines @@
   //  specification.
   //  After a valid "T" has been read while scanning an ES5 datetime string,
   //  the input can no longer be a valid legacy date, since the "T" is a
   //  garbage string after a number has been read.
 
   // First try getting as far as possible with as ES5 Date Time String.
   DateToken next_unhandled_token = ParseES5DateTime(&scanner, &day, &time, &tz);
   if (next_unhandled_token.IsInvalid()) return false;
   bool has_read_number = !day.IsEmpty();
   // If there's anything left, continue with the legacy parser.
-  bool legacy_parser = !next_unhandled_token.IsEndOfInput();
+  bool legacy_parser = false;
   for (DateToken token = next_unhandled_token;
        !token.IsEndOfInput();
        token = scanner.Next()) {
     if (token.IsNumber()) {
+      legacy_parser = true;
       has_read_number = true;
       int n = token.number();
       if (scanner.SkipSymbol(':')) {
         if (scanner.SkipSymbol(':')) {
           // n + "::"
           if (!time.IsEmpty()) return false;
           time.Add(n);
           time.Add(0);
         } else {
           // n + ":"
@@ skipping 15 matching lines @@
         DateToken peek = scanner.Peek();
         if (!peek.IsEndOfInput() &&
             !peek.IsWhiteSpace() &&
             !peek.IsKeywordZ() &&
             !peek.IsAsciiSign()) return false;
       } else {
         if (!day.Add(n)) return false;
         scanner.SkipSymbol('-');
       }
     } else if (token.IsKeyword()) {
+      legacy_parser = true;
       // Parse a "word" (sequence of chars. >= 'A').
       KeywordType type = token.keyword_type();
       int value = token.keyword_value();
       if (type == AM_PM && !time.IsEmpty()) {
         time.SetHourOffset(value);
       } else if (type == MONTH_NAME) {
         day.SetNamedMonth(value);
         scanner.SkipSymbol('-');
       } else if (type == TIME_ZONE_NAME && has_read_number) {
         tz.Set(value);
       } else {
         // Garbage words are illegal if a number has been read.
         if (has_read_number) return false;
         // The first number has to be separated from garbage words by
         // whitespace or other separators.
         if (scanner.Peek().IsNumber()) return false;
       }
     } else if (token.IsAsciiSign() && (tz.IsUTC() || !time.IsEmpty())) {
+      legacy_parser = true;
       // Parse UTC offset (only after UTC or time).
       tz.SetSign(token.ascii_sign());
       // The following number may be empty.
       int n = 0;
       int length = 0;
       if (scanner.Peek().IsNumber()) {
         DateToken token = scanner.Next();
         length = token.length();
         n = token.number();
       }
@@ skipping 198 matching lines @@
   if (tz->IsEmpty()) tz->Set(0);
   day->set_iso_date();
   return DateToken::EndOfInput();
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DATEPARSER_INL_H_