If the finger enrollment fails (see b/119131588 for an example case), biod emits a "SessionFailed" signal (and biod considers the EnrollSession as "ended").

The fingerprint UI does not seem to handle this case (it still shows the "Registering Fingerprint" screen).


Sample dbus output:

dbus-monitor --system | grep  "org.chromium.BiometricsDaemon"

method call time=1544131318.542073 sender=:1.118 -> destination=org.chromium.BiometricsDaemon serial=25101 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager/AuthSession; interface=org.chromium.BiometricsDaemon.AuthSession; member=End
method call time=1544131318.554592 sender=:1.118 -> destination=org.chromium.BiometricsDaemon serial=25102 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=StartEnrollSession
   object path "/org/chromium/BiometricsDaemon/CrosFpBiometricsManager/EnrollSession"
signal time=1544131326.245689 sender=:1.107 -> destination=(null destination) serial=82 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131327.019497 sender=:1.107 -> destination=(null destination) serial=83 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131327.777501 sender=:1.107 -> destination=(null destination) serial=84 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131328.431451 sender=:1.107 -> destination=(null destination) serial=85 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131329.075791 sender=:1.107 -> destination=(null destination) serial=86 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131329.729419 sender=:1.107 -> destination=(null destination) serial=87 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131330.375102 sender=:1.107 -> destination=(null destination) serial=88 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131330.900423 sender=:1.107 -> destination=(null destination) serial=89 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131331.426406 sender=:1.107 -> destination=(null destination) serial=90 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=EnrollScanDone
signal time=1544131331.962666 sender=:1.107 -> destination=(null destination) serial=91 path=/org/chromium/BiometricsDaemon/CrosFpBiometricsManager; interface=org.chromium.BiometricsDaemon.BiometricsManager; member=SessionFailed