[Nexus 6P Q&A, Help & Troubleshooting] motoridersd:
Found another culprit. It's the Five Stars app, which is a rewards thing that I use to track points at a local Ramen Place. I install this app on and off, so this would explain why I would have the drain before. I never thought this would cause it. This app causes the phone to do a BLE scan constantly when the process com.fivestars.FiveStarsConsumer is running. Looks like this in logcat:

02-15 10:00:04.020 15941 15941 D BluetoothAdapter: STATE_ON
02-15 10:00:04.022 9529 9610 D BtGatt.GattService: stopScan() - queue size =1
02-15 10:00:04.023 9529 9553 D BtGatt.ScanManager: stop scan
02-15 10:00:04.026 9529 16447 D BtGatt.GattService: unregisterClient() - clientIf=7
02-15 10:00:04.029 15941 15941 D BluetoothAdapter: STATE_ON
02-15 10:00:04.036 9529 9539 D BtGatt.GattService: registerClient() - UUID=f809006f-f999-40f3-a083-7dbdf47035ac
02-15 10:00:04.037 9529 9550 D BtGatt.GattService: onClientRegistered() - UUID=f809006f-f999-40f3-a083-7dbdf47035ac, clientIf=7
02-15 10:00:04.038 15941 15951 D BluetoothLeScanner: onClientRegistered() - status=0 clientIf=7
02-15 10:00:04.039 9529 9610 D BtGatt.GattService: start scan with filters
02-15 10:00:04.044 9529 9550 D BtGatt.GattService: onScanFilterParamsConfigured() - clientIf=7, status=0, action=1, availableSpace=32
02-15 10:00:04.044 9529 9550 D BtGatt.ScanManager: callback done for clientIf - 7 status - 0
02-15 10:00:04.044 9529 9553 D BtGatt.ScanManager: configureRegularScanParams() - queue=0
02-15 10:00:04.044 9529 9553 D BtGatt.ScanManager: configureRegularScanParams() - ScanSetting Scan mode=-2147483648 mLastConfiguredScanSetting=2
02-15 10:00:04.045 9529 9553 D BtGatt.ScanManager: configureRegularScanParams() - queue emtpy, scan stopped
02-15 10:00:04.050 9529 9553 D BtGatt.ScanManager: handling starting scan
02-15 10:00:04.061 9529 9550 D BtGatt.GattService: onScanFilterEnableDisabled() - clientIf=7, status=0, action=1
02-15 10:00:04.061 9529 9550 D BtGatt.ScanManager: callback done for clientIf - 7 status - 0
02-15 10:00:04.062 9529 9553 D BtGatt.ScanManager: addFilterToController: 5
02-15 10:00:04.069 9529 9550 D BtGatt.GattService: onScanFilterConfig() - clientIf=7, action = 0 status = 0, filterType=5, availableSpace=47
02-15 10:00:04.069 9529 9550 D BtGatt.ScanManager: callback done for clientIf - 7 status - 0
02-15 10:00:04.070 9529 9553 D BtGatt.ScanManager: configureFilterParamter 500 10000 1 0
02-15 10:00:04.076 9529 9550 D BtGatt.GattService: onScanFilterParamsConfigured() - clientIf=7, status=0, action=0, availableSpace=31
02-15 10:00:04.076 9529 9550 D BtGatt.ScanManager: callback done for clientIf - 7 status - 0
02-15 10:00:04.077 9529 9553 D BtGatt.ScanManager: addFilterToController: 5
02-15 10:00:04.083 9529 9550 D BtGatt.GattService: onScanFilterConfig() - clientIf=7, action = 0 status = 0, filterType=5, availableSpace=46
02-15 10:00:04.083 9529 9550 D BtGatt.ScanManager: callback done for clientIf - 7 status - 0
02-15 10:00:04.084 9529 9553 D BtGatt.ScanManager: configureFilterParamter 500 10000 1 0
02-15 10:00:04.090 9529 9550 D BtGatt.GattService: onScanFilterParamsConfigured() - clientIf=7, status=0, action=0, availableSpace=30
02-15 10:00:04.090 9529 9550 D BtGatt.ScanManager: callback done for clientIf - 7 status - 0
02-15 10:00:04.090 9529 9553 D BtGatt.ScanManager: configureRegularScanParams() - queue=1
02-15 10:00:04.090 9529 9553 D BtGatt.ScanManager: configureRegularScanParams() - ScanSetting Scan mode=0 mLastConfiguredScanSetting=-2147483648
02-15 10:00:04.091 9529 9553 D BtGatt.ScanManager: configureRegularScanParams - scanInterval = 8000configureRegularScanParams - scanWindow = 800
02-15 10:00:04.092 9529 9550 D BtGatt.GattService: onScanParamSetupCompleted : 0

I manually killed the process and it stopped, and confirmed it came back after launching the app again. All this with the screen off.