At my schools we preach the importance of the 20-foot putting stroke since 20 feet is the most common putt length in golf. So any student of mine facing a 15-foot putt on the course will preview some small adjustment to that 20-foot reference stroke during their pre-putt routine factoring in the other conditions of the putt that are computed as you read the green such as slope break grain wind etc.
So what do you do? You pick the shot type you want to hit and choose your wedge. Then you take preview swings near the ball to test the lie conditions and gauge the length of swing needed to knock the ball close.
At the same time the existing contours and slopes on these greens have remained unchanged. This combination of smoother faster surfaces with consistent slopes (not to mention less aggressive grooves on your wedges thanks to rules changes) has made it crucial that golfers possess a soft deft touch with their short clubs if they want to successfully handle superfast downhill pitch and chip shots.