If you've flashed Android N's second developer preview and ventured into the battery section of the settings, you may have noticed something odd happening with the History details screen (the one what shows up when you tap the graph) which normally has the expanded battery drain graph with the different components' usage. The latter part is nowhere to be seen in Dev Preview 2.
The graph is still there, but it's stretched across the screen and there's none of the information below it. No cellular signal, no GPS, no Wi-Fi, no device awake, no screen on, and no charging. All of it is poof, gone. Thankfully, this isn't a permanent change, but a bug in this developer preview. Artem filed an issue on the bug tracker, which was closed because it isn't replicated in future previews.
Small bug, short lived. We can safely move on.