As above, the guidelines for trained personnel do still include rescue breaths, but - also as above - the are other considerations such as the cause of the cardiac arrest, reversible causes, hospital vs out of hospital, who is available and their level of training, the situation as regards the likelihood of emergency services arriving soon, how long the resus attempt has been going on for etc. etc..
Regardless of the situation (assuming a defib is not immediately available or the rhythm is not shockable) the prompt start and quality of chest compressions is the prime factor in improving outcomes. Rescue breaths are of secondary importance, particularly as chest compressions are all too often started late, not at all, or carried out poorly.
Hence the content of the recent Vinnie Jones ads.
I had a chat to one of our resus team earlier about the situation I am envisaging (that is, remote location, possibly at night, first trained person on scene, and ambulance a long way away). That's a pretty hopeless situation, of course. A pocket mask remains something I'd carry if I, personally, was doing any ride that involved possibly being further away than I'd like from emergency services.