Chrome's PDF viewer lacks the basic features one expects from a PDF viewer. It doesn't make sense to abandon the concept of pages or not support ToC. Those things are essential in PDFs. pdf.js handles all of those things. And there were browsers being able to display PDF before Chrome. KDE's Konqueror could simply load KPDF and Safari had Preview.app embedded.

I wish Google would abandon their viewer (which is closed source btw) and rather start using and contributing to pdf.js.