message: Fix possible buffer over-read in RewriteDriver::ParseTextInternal
  When RewriteDriver::ShouldSkipParsing returns true, Write is
  called with content without size. This results in conversion
  of content to StringPiece and relying on strlen to determine
  size. This could result in buffer over-read if content is
  not NULL-terminated.
  Fixes
diff: @@ -2178,7 +2178,8 @@ bool RewriteDriver::StartParseId(const StringPiece& url, const StringPiece& id,
  void RewriteDriver::ParseTextInternal(const char* content, int size) {
  num_bytes_in_ += size;
  if (ShouldSkipParsing()) {
  - writer()->Write(content, message_handler());
  + StringPiece sp(content, size);
  + writer()->Write(sp, message_handler());
  } else if (debug_filter_ != NULL) {
  debug_filter_->StartParse();
  HtmlParse::ParseTextInternal(content, size);
  