Behold, a unit test for Scanner::BookmarkScope (& scanner bookmarking).

src/parsing/scanner.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.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #ifndef V8_PARSING_SCANNER_H_
 #define V8_PARSING_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 824 matching lines @@
   //       [current_] [next_] c0_ |      [scanner state]
   // So when the scanner is logically at the beginning of an expression
   // like "1234 + 4567", then:
   // - current_ contains "1234"
   // - next_ contains "+"
   // - c0_ contains ' ' (the space between "+" and "5678",
   // - the source_ character stream points to the beginning of "5678".
   // To be able to restore this state, we will keep copies of current_, next_,
   // and c0_; we'll ask the stream to bookmark itself, and we'll copy the
   // contents of current_'s and next_'s literal buffers to bookmark_*_literal_.
-  static const uc32 kNoBookmark = -1;
-  static const uc32 kBookmarkWasApplied = -2;
+  static const uc32 kNoBookmark = -2;
+  static const uc32 kBookmarkWasApplied = -3;
   uc32 bookmark_c0_;
   TokenDesc bookmark_current_;
   TokenDesc bookmark_next_;
   LiteralBuffer bookmark_current_literal_;
   LiteralBuffer bookmark_current_raw_literal_;
   LiteralBuffer bookmark_next_literal_;
   LiteralBuffer bookmark_next_raw_literal_;
 
   // Input stream. Must be initialized to an Utf16CharacterStream.
   Utf16CharacterStream* source_;
@@ skipping 18 matching lines @@
   bool found_html_comment_;
 
   MessageTemplate::Template scanner_error_;
   Location scanner_error_location_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_SCANNER_H_