A decimal integer literal with a leading 0 is now an error in strict mode.

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/ast.h"
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
@@ skipping 836 matching lines @@
     }
     return false;
   }
 
   bool PeekInOrOf() {
     return peek() == Token::IN || PeekContextualKeyword(CStrVector("of"));
   }
 
   // Checks whether an octal literal was last seen between beg_pos and end_pos.
   // If so, reports an error. Only called for strict mode and template strings.
-  void CheckOctalLiteral(int beg_pos, int end_pos,
-                         MessageTemplate::Template message, bool* ok) {
+  void CheckOctalLiteral(int beg_pos, int end_pos, bool is_template_escape,
+                         bool* ok) {
     Scanner::Location octal = scanner()->octal_position();
     if (octal.IsValid() && beg_pos <= octal.beg_pos &&
         octal.end_pos <= end_pos) {
+      MessageTemplate::Template message =
+          is_template_escape ? MessageTemplate::kTemplateOctalLiteral
+                             : scanner()->octal_message();
+      DCHECK_NE(message, MessageTemplate::kNone);

[Dan Ehrenberg, 2016/11/18 17:13:51]

IMO it wouldn't hurt to continue updating the UseCounter here, just to be sure
it doesn't break a bunch of sites in the future, but maintaining the counters 
is optional and not something we've done consistently in the past.

       impl()->ReportMessageAt(octal, message);
       scanner()->clear_octal_position();
       *ok = false;
     }
   }
-  // for now, this check just collects statistics.
-  void CheckDecimalLiteralWithLeadingZero(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();
-      impl()->CountUsage(v8::Isolate::kDecimalWithLeadingZeroInStrictMode);
-    }
-  }
 
   inline void CheckStrictOctalLiteral(int beg_pos, int end_pos, bool* ok) {
-    CheckOctalLiteral(beg_pos, end_pos, MessageTemplate::kStrictOctalLiteral,
-                      ok);
+    CheckOctalLiteral(beg_pos, end_pos, false, ok);
   }
 
   inline void CheckTemplateOctalLiteral(int beg_pos, int end_pos, bool* ok) {
-    CheckOctalLiteral(beg_pos, end_pos, MessageTemplate::kTemplateOctalLiteral,
-                      ok);
+    CheckOctalLiteral(beg_pos, end_pos, true, ok);
   }
 
   void CheckDestructuringElement(ExpressionT element, int beg_pos, int end_pos);
 
   // Checking the name of a function literal. This has to be done after parsing
   // the function, since the function can declare itself strict.
   void CheckFunctionName(LanguageMode language_mode, IdentifierT function_name,
                          FunctionNameValidity function_name_validity,
                          const Scanner::Location& function_name_loc, bool* ok) {
     if (function_name_validity == kSkipFunctionNameCheck) return;
@@ skipping 4550 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H