UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3030.0 Safari/537.36

Steps to reproduce the problem:
1.Set pinned tab as startup page. 
2. Restart browser 
3.Both pinned tab and additional full tab open 

What is the expected behavior?
Just pinned tab opens.

What went wrong?
Additional full tab opens with pinned tab set as startup page.

Did this work before? Yes 58.0.3029.3

Chrome version: 59.0.3030.0  Channel: canary
OS Version: 10.0
Flash Version: 25.0.0.127

Issue has been present in Chromium snapshots for quite a while but just bled into Canary.