[parser, serializer] Fix more -Wsign-compare warnings.

src/parsing/scanner.cc

Index: src/parsing/scanner.cc
diff --git a/src/parsing/scanner.cc b/src/parsing/scanner.cc
index cfc0410b83cc77cbb78984aba151113d94429633..363ab7dfe9915091bae9b1bb7fcbf85b2ad1e8d6 100644
--- a/src/parsing/scanner.cc
+++ b/src/parsing/scanner.cc
@@ -59,7 +59,7 @@ void Scanner::BookmarkScope::Apply() {
   } else {
     scanner_->SeekNext(bookmark_);
     scanner_->Next();
-    DCHECK_EQ(scanner_->location().beg_pos, bookmark_);
+    DCHECK_EQ(scanner_->location().beg_pos, static_cast<int>(bookmark_));
   }
   bookmark_ = kBookmarkWasApplied;
 }
@@ -1638,7 +1638,7 @@ void Scanner::SeekNext(size_t position) {
   // 3, re-scan, by scanning the look-ahead char + 1 token (next_).
   c0_ = source_->Advance();
   Next();
-  DCHECK_EQ(next_.location.beg_pos, position);
+  DCHECK_EQ(next_.location.beg_pos, static_cast<int>(position));
 }
 
 }  // namespace internal