Doesn't show any notifications

I can confirm that this doesn't work in 15.0.874.106 stable either.

Any progress on this bug? I really would like to have the pretty notification bubbles back in Chrome.

Check if doing something like:

ldd ~/.config/chromium/Default/Extensions/nmgdlklj*/2.3.0_0/bin/$(dpkg --print-architecture)/npchromifyosd.so | grep "not found"

Doesn't return to you this:
   libnotify.so.1 => not found

In that case you just need to link your libnotify.so.4 to a symlink libnotify.so.1
I'm not sure if doing this on that folder is enough, so I did this:

For amd64:
  sudo ln -s /usr/lib/x86_64-linux-gnu/libnotify.so.4 /usr/lib/x86_64-linux-gnu/libnotify.so.1

For i386:
  sudo ln -s /usr/lib/i386-linux-gnu/libnotify.so.4 /usr/lib/i386-linux-gnu/libnotify.so.1

Sorry for such a late reply. I did try the command you posted, I did get the "not found" so made the link to the file. After that the notifications still don't work.
Running the first command again doesn't show any not found now, obviously. The test webpage that I posted for the first time is not working apparently, so I've used other pages and even a cached version of that page, but nothing.

Is there something else I can do?

After trying many things, I decided to delete the whole configuration file of Chrome. I installed the add-on for the first time again, run it and didn't work. Run the commands you posted so I can link the library file and now it's working! I guess there was some configuration error somewhere.

I would recommend submitting a fix so that user don't have to manually link the library file like I had to do.
I think we should leave the bug open until a proper fixed version is released instead of a workaround.

There's a fork of this extension that works for the current version of Ubuntu:
https://github.com/tualatrix/LinuxNativeNotification

link your libnotify.so.4 to a symlink libnotify.so.1 works for me, sounds like an easy patch