I also had issues with Ubuntu 14.04's build of Chromium 41, so I installed Google Chrome :( and that worked.
on my Fedora 21 build of Chromium 40 I got the error 'Manifest file is invalid' when trying install the extension, even after clearing data and reloading the extension. This will take a while as it seems to download a crx installer weighing in at 113Mb, and another one at around 9Mb, so be patient: Install from here - click 'Add to Chrome' Here are some steps I did to get it to work
You can now under Chrome run APKs, using this extension (bearing in mind it is in development for use by developers for testing apps).