Add UseCounter for decimal with leading zero.

src/parsing/parser-base.h

 // Copyright 2012 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_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/hashmap.h"
@@ skipping 600 matching lines @@
   void CheckOctalLiteral(int beg_pos, int end_pos,
                          MessageTemplate::Template message, bool* ok) {
     Scanner::Location octal = scanner()->octal_position();
     if (octal.IsValid() && beg_pos <= octal.beg_pos &&
         octal.end_pos <= end_pos) {
       ReportMessageAt(octal, message);
       scanner()->clear_octal_position();
       *ok = false;
     }
   }
+  // for now, this check just collects statistics.
+  void CheckDecimalLiteralWithLeadingZero(int* use_counts, int beg_pos,
+                                          int end_pos) {
+    Scanner::Location token_location =
+        scanner()->decimal_with_leading_zero_position();
+    if (token_location.IsValid() && beg_pos <= token_location.beg_pos &&
+        token_location.end_pos <= end_pos) {
+      scanner()->clear_decimal_with_leading_zero_position();
+      if (use_counts != nullptr)
+        ++use_counts[v8::Isolate::kDecimalWithLeadingZeroInStrictMode];
+    }
+  }
 
   inline void CheckStrictOctalLiteral(int beg_pos, int end_pos, bool* ok) {
     CheckOctalLiteral(beg_pos, end_pos, MessageTemplate::kStrictOctalLiteral,
                       ok);
   }
 
   inline void CheckTemplateOctalLiteral(int beg_pos, int end_pos, bool* ok) {
     CheckOctalLiteral(beg_pos, end_pos, MessageTemplate::kTemplateOctalLiteral,
                       ok);
   }
@@ skipping 2680 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H