Estoy tratando de incorporar la API de caras de Google Play Services 7.8 en mi aplicación, pero cada vez que trato de detectar caras me da el error:

FaceDetectorHandle detector Detector de rostro nativo aún no disponible. Volviendo a la detección sin operación

De acuerdo al final de la publicaciónDetección de rostros Android-er, este problema se produce en dispositivos con Lollipop o posterior. Específicamente, dijeron que funciona en un "RedMi 2, con Android 4.4.4 con los servicios de Google Play versión 7.8.99 instalados, pero no en un Nexus 7 2012 (SIN cámara frontal) con Android 5.1.1, con el mismo Google Play servicios versión 7.8.99 instalada ". Tampoco funciona en mi OnePlus One con 5.0.2. ¿Alguien sabe la causa o la solución? ¿Eventualmente instalará la biblioteca y funcionará?

Editar: Aquí hay algunos registros. Simplemente copié los registros de advertencia y más arriba en el momento en que se usó el detector de rostros, por lo que podría no ser relevante.

08-19 17:29:17.828 W/ResourcesManager(25536): Asset path '/system/framework/com.android.media.remotedisplay.jar' does not exist or contains no resources.
08-19 17:29:17.828 W/ResourcesManager(25536): Asset path '/system/framework/com.android.location.provider.jar' does not exist or contains no resources.
08-19 17:29:17.908 W/FaceDetectorHandle(25536): Native face detector not yet available.  Reverting to no-op detection.
08-19 17:29:18.060 W/ResourcesManager(25536): Asset path '/system/framework/com.android.media.remotedisplay.jar' does not exist or contains no resources.
08-19 17:29:18.060 W/ResourcesManager(25536): Asset path '/system/framework/com.android.location.provider.jar' does not exist or contains no resources.
08-19 17:29:20.267 W/LatinIME( 1645): Deprecated private IME option specified: nm,com.google.android.inputmethod.latin.noGestureFloatingPreview
08-19 17:29:20.267 W/LatinIME( 1645): Use com.google.android.inputmethod.latin.noMicrophoneKey instead
08-19 17:29:20.294 E/EntSec  (  923): [QSB   ] [QSB_CLIENT ] No connection with the NQS
08-19 17:29:20.306 E/EntSec  (  923): [QSB   ] [QSB_CLIENT ] No connection with the NQS
08-19 17:29:20.317 E/EntSec  (  923): [QSB   ] [QSB_CLIENT ] No connection with the NQS
08-19 17:29:20.532 E/EntSec  (  923): [QSB   ] [QSB_CLIENT ] No connection with the NQS
08-19 17:29:20.655 W/OpenGLRenderer( 1814): Incorrectly called buildLayer on View: CoreSuggestionView, destroying layer...
08-19 17:29:20.655 W/OpenGLRenderer( 1814): Incorrectly called buildLayer on View: CoreSuggestionView, destroying layer...
08-19 17:29:20.655 W/OpenGLRenderer( 1814): Incorrectly called buildLayer on View: CoreSuggestionView, destroying layer...
08-19 17:29:20.655 W/OpenGLRenderer( 1814): Incorrectly called buildLayer on View: NowProgressBar, destroying layer...
08-19 17:29:20.655 W/OpenGLRenderer( 1814): Incorrectly called buildLayer on View: CrossfadingWebImageView, destroying layer...
08-19 17:29:20.655 W/OpenGLRenderer( 1814): Incorrectly called buildLayer on View: ew, destroying layer...
08-19 17:29:20.912 W/LatinIME( 1645): Deprecated private IME option specified: nm,com.google.android.inputmethod.latin.noGestureFloatingPreview
08-19 17:29:20.912 W/LatinIME( 1645): Use com.google.android.inputmethod.latin.noMicrophoneKey instead
08-19 17:29:20.924 E/EntSec  (  923): [QSB   ] [QSB_CLIENT ] No connection with the NQS
08-19 17:29:20.934 W/Search.SearchUrlHelper( 1969): URL param or header with a key: "oq" has an empty value.
08-19 17:29:20.941 E/EntSec  (  923): [QSB   ] [QSB_CLIENT ] No connection with the NQS
08-19 17:29:20.956 E/EntSec  (  923): [QSB   ] [QSB_CLIENT ] No connection with the NQS
08-19 17:29:21.038 W/IInputConnectionWrapper( 1814): performPrivateCommand on inactive InputConnection
08-19 17:29:21.085 W/BindingManager( 1969): Cannot call determinedVisibility() - never saw a connection for the pid: 1969
08-19 17:29:21.764 W/VelvetPresenter( 1969): Still observing while not the active client
08-19 17:29:21.765 W/VelvetPresenter( 1969): Still observing while not the active client
08-19 17:29:22.067 W/BindingManager( 1969): Cannot call determinedVisibility() - never saw a connection for the pid: 1969
08-19 17:29:22.250 W/WebViewRenderState( 1969): resultsPageEnd: not current commit, new=27, committed=0
08-19 17:29:22.344 W/SurfaceFlinger(  243): couldn't log to binary event log: overflow.
08-19 17:29:22.371 W/OpenGLRenderer( 1814): Incorrectly called buildLayer on View: ew, destroying layer...
08-19 17:29:22.462 E/WebViewWorkerImpl( 1969): onShowedSrp: No SearchResult found being shown in WebView.
08-19 17:29:26.635 W/FaceDetector(25536): FaceDetector was not released with FaceDetector.release()