1) Open Command Prompt with "Run as Administrator"
2) Run this command to kill all Chrome processes:
C:\Windows\System32\taskkill.exe /F /IM chrome.exe
3) Navigate to:
C:\Users\<Username>\AppData\Local\Google\
4) rename the "Chrome" folder to "Chrome-old"
5) restore your backup of the Chrome folder (it can be pretty big, mine was 7 gb)
6) relaunch Chrome.... voila, OneTab history is back!