Fix Scanner invariants w/ literal buffers.

src/parsing/scanner.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.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #include "src/parsing/scanner.h"
 
 #include <stdint.h>
 
@@ skipping 1580 matching lines @@
   }
   return false;
 }
 
 
 void Scanner::ResetToBookmark() {
   DCHECK(BookmarkHasBeenSet());  // Caller hasn't called SetBookmark.
 
   source_->ResetToBookmark();
   c0_ = bookmark_c0_;
-  StartLiteral();
-  StartRawLiteral();
-  CopyTokenDesc(&next_, &bookmark_current_);
+  CopyToNextTokenDesc(&bookmark_current_);
   current_ = next_;
-  StartLiteral();
-  StartRawLiteral();
-  CopyTokenDesc(&next_, &bookmark_next_);
-
+  CopyToNextTokenDesc(&bookmark_next_);
   bookmark_c0_ = kBookmarkWasApplied;
 }
 
 
 bool Scanner::BookmarkHasBeenSet() { return bookmark_c0_ >= 0; }
 
 
 bool Scanner::BookmarkHasBeenReset() {
   return bookmark_c0_ == kBookmarkWasApplied;
 }
 
 
 void Scanner::DropBookmark() { bookmark_c0_ = kNoBookmark; }
 
+void Scanner::CopyToNextTokenDesc(TokenDesc* from) {
+  StartLiteral();
+  StartRawLiteral();
+  CopyTokenDesc(&next_, from);
+  if (next_.literal_chars->length() == 0) next_.literal_chars = nullptr;
+  if (next_.raw_literal_chars->length() == 0) next_.raw_literal_chars = nullptr;
+}
 
 void Scanner::CopyTokenDesc(TokenDesc* to, TokenDesc* from) {
   DCHECK_NOT_NULL(to);
   DCHECK_NOT_NULL(from);
   to->token = from->token;
   to->location = from->location;
   to->literal_chars->CopyFrom(from->literal_chars);
   to->raw_literal_chars->CopyFrom(from->raw_literal_chars);
 }
 
@@ skipping 132 matching lines @@
     backing_store_.Add(static_cast<uint8_t>((one_byte_length >> 7) | 0x80u));
   }
   backing_store_.Add(static_cast<uint8_t>(one_byte_length & 0x7f));
 
   backing_store_.AddBlock(bytes);
   return backing_store_.EndSequence().start();
 }
 
 }  // namespace internal
 }  // namespace v8