Do not save/restore AST id generator.

src/preparser.cc

 // 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.
 
 #include <cmath>
 
 #include "include/v8stdint.h"
 
 #include "src/allocation.h"
 #include "src/base/logging.h"
@@ skipping 14 matching lines @@
 // Usually defined in math.h, but not in MSVC until VS2013+.
 // Abstracted to work
 int isfinite(double value);
 
 }  // namespace std
 #endif
 
 namespace v8 {
 namespace internal {
 
-class PreParserTraits::Checkpoint
-    : public ParserBase<PreParserTraits>::CheckpointBase {
- public:
-  explicit Checkpoint(ParserBase<PreParserTraits>* parser)
-      : ParserBase<PreParserTraits>::CheckpointBase(parser) {}
-};
-
 void PreParserTraits::ReportMessageAt(Scanner::Location location,
                                       const char* message,
                                       const char* arg,
                                       bool is_reference_error) {
   ReportMessageAt(location.beg_pos,
                   location.end_pos,
                   message,
                   arg,
                   is_reference_error);
 }
@@ skipping 899 matching lines @@
   ParseIdentifier(kAllowEvalOrArguments, CHECK_OK);
   ParseArguments(ok);
 
   return Expression::Default();
 }
 
 #undef CHECK_OK
 
 
 } }  // v8::internal