Parser: Make skipping HTML comments optional.

src/parsing/scanner.h

Index: src/parsing/scanner.h
diff --git a/src/parsing/scanner.h b/src/parsing/scanner.h
index 9f195e3657fae6e90a2417f52ba6e0497c80a504..3e3bb93fb6a59668f8660df2adbe7ac9c0ba4e0c 100644
--- a/src/parsing/scanner.h
+++ b/src/parsing/scanner.h
@@ -340,7 +340,7 @@ class Scanner {
   // -1 is outside of the range of any real source code.
   static const int kNoOctalLocation = -1;
 
-  explicit Scanner(UnicodeCache* scanner_contants);
+  Scanner(UnicodeCache* scanner_contants, bool ignore_html_comments);
 
   void Initialize(Utf16CharacterStream* source);
 
@@ -755,6 +755,8 @@ class Scanner {
   // Whether there is a multi-line comment that contains a
   // line-terminator after the current token, and before the next.
   bool has_multiline_comment_before_next_;
+  // Whether to skip HTML comments (or report them as errors).
+  bool ignore_html_comments_;
 
   // Whether this scanner encountered an HTML comment.
   bool found_html_comment_;