camera2: Fix CameraMetadata#getKeys

import android.hardware.camera2.impl.CameraMetadataNative;

import java.lang.reflect.Field;

import java.lang.reflect.Modifier;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

        Field[] fields = type.getDeclaredFields();

        for (Field field : fields) {

            if (field.getDeclaringClass().isAssignableFrom(Key.class)) {

            // Filter for Keys that are public

            if (field.getType().isAssignableFrom(Key.class) &&

                    (field.getModifiers() & Modifier.PUBLIC) != 0) {

                Key<?> key;

                try {

                    key = (Key<?>) field.get(instance);

    @Override

    public <T> T get(Key<T> key) {

        if (key == STATISTICS_FACES) { // Don't throw IllegalArgumentException

            // TODO: Implement android.statistics.faces

            return null;

        }

        return mResults.get(key);

    }