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

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 41 matching lines @@
                   : scanner_->location().beg_pos;
 }
 
 void Scanner::BookmarkScope::Apply() {
   DCHECK(HasBeenSet());  // Caller hasn't called SetBookmark.
   if (bookmark_ == kBookmarkAtFirstPos) {
     scanner_->SeekNext(0);
   } 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;
 }
 
 bool Scanner::BookmarkScope::HasBeenSet() {
   return bookmark_ != kNoBookmark && bookmark_ != kBookmarkWasApplied;
 }
 
 bool Scanner::BookmarkScope::HasBeenApplied() {
   return bookmark_ == kBookmarkWasApplied;
@@ skipping 1558 matching lines @@
   //    (next_ + next_next_ will be overwrittem by Next(),
   //     current_ will remain unchanged, so overwrite it fully.)
   current_ = {{0, 0}, nullptr, nullptr, 0, Token::UNINITIALIZED};
   next_.token = Token::UNINITIALIZED;
   next_next_.token = Token::UNINITIALIZED;
   // 2, reset the source to the desired position,
   source_->Seek(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
 }  // namespace v8