Chrome version : 51.0.2687.0 5ee3f242cefebba7eb0f05424e7308f9158d8388-refs/heads/master@{#382459} 32/64 bit
OS : Windows (Win 7 aero enabled), Linux

Steps : 
1. Launch Chrome and go to chrome://apps. 
2. Right click on YouTube icon and select App info option.
3. Now move the focus on 'Open in a Tab' drop down using Tab and press Space Bar or Enter key, observe.

Actual : 'Open in a tab' drop down list does not open using Space Bar or Enter key.
Expected : The drop down list should open using either Space Bar or Enter key.

This is a non regression seen from 'M-43', series as this is a new feature introduced in 43.0.2316.0

Change log info : 
https://chromium.googlesource.com/chromium/src/+log/43.0.2315.0..43.0.2316.0?pretty=fuller&n=10000

Suspecting : 318163

@tsergeant : Could you please take a look for this issue?

Note : The above issue is not reproducible on Mac OS.
 

Deleted: Actual_app_info.mp4 582 KB

Actual_app_info.mp4 582 KB Download