How Do I Enable The "chrome.downloads" Api On The Dev Or Canary Channels?

I was hoping to do some experimentation with the chrome.downloads api. I downloaded the dev and canary versions of Chrome and created a new extension with the downloads permission,

Solution 1:

You are probably seeing two unrelated bugs in action. The empty notification is https://code.google.com/p/chromium/issues/detail?id=181191, which is preventing you from seeing the contents: "Downloads Overwrite Existing Files has crashed. Click this balloon to reload the extension." This bug cropped up very recently, and we're looking at it now.

The other bug, as you've probably guessed, is that crash. I just filed it here: https://code.google.com/p/chromium/issues/detail?id=197926.

Sorry for the trouble. This is part of the fun of running on some of the more "exciting" channels. This is a pretty lame answer to your question because it doesn't get you unblocked, but it is a correct explanation of what's going on.