Additional immutable check for rowObjects
Additional immutable check for rowObjects

Auditors: @bsclifton

Test Plan:
1. go to "about:history"
2. do not select anything
3. right click on an arbitrary entry
4. context menu should show

willy-b/browser-laptop,timborden/browser-laptop,willy-b/browser-laptop,luixxiul/browser-laptop,luixxiul/browser-laptop,Sh1d0w/browser-laptop,jonathansampson/browser-laptop,darkdh/browser-laptop,darkdh/browser-laptop,Sh1d0w/browser-laptop,jonathansampson/browser-laptop,dcposch/browser-laptop,diasdavid/browser-laptop,pmkary/braver,dcposch/browser-laptop,diasdavid/browser-laptop,diasdavid/browser-laptop,dcposch/browser-laptop,jonathansampson/browser-laptop,timborden/browser-laptop,timborden/browser-laptop,Sh1d0w/browser-laptop,timborden/browser-laptop,luixxiul/browser-laptop,jonathansampson/browser-laptop,pmkary/braver,darkdh/browser-laptop,diasdavid/browser-laptop,pmkary/braver,willy-b/browser-laptop,dcposch/browser-laptop,willy-b/browser-laptop,luixxiul/browser-laptop,darkdh/browser-laptop,Sh1d0w/browser-laptop,pmkary/braver