On Ubuntu Gnome 14.10 and Sabayon with Gnome Shell I encountered the following situation when launching Google Chrome or Chromium after computer boot - the browsers would say:
"Google Chrome didn't shut down correctly"
"Chromium didn't shut down correctly"
and would offer to restore the previous tabs. Of course, the browsers had been shut down correctly before powering off the system.
Well, the cause of the error turned out to be simpler than I thought:
To stop getting the error uncheck "Continue running background apps when Chromim (Chrome) is closed".
In case you need to allow running background apps in the browsers, well, browse their respective bug-trackers for a relevant bug report and see if there are other solutions, workarounds, etc.