DsyMnapTic
Android Expert
On most modern chargers, I do believe they have a sensor built in to trickle the charge. Also, on one of the more recent studies I've seen, the short-term effects of overcharging (leaving the phone on the charger for hours after it's been at 100%) are very little. Up to even a few months of this, there isn't much in the way of adverse effects. However, long-term, 6 months to a year or more of this, there's an exponential increase of damage that can be done. But probably for the foreseeable future of having this phone, you'd be alright.
I just read a pretty good thread over on android central and most people there are saying that the phone basically tells the battery to stop charging once it hits 100. Then the phone just runs off of the AC current from the charger and periodically kicks the battery charging back in as the battery drains. So seemingly it's all handled by the phone.