Fix unmount up button

Change-Id: I24b388079c438075e3a8652822e7a2fb84fec608
Fixes: 28704198
diff --git a/src/com/android/settings/deviceinfo/PrivateVolumeUnmount.java b/src/com/android/settings/deviceinfo/PrivateVolumeUnmount.java
index 5a4c7b1..7032a1d 100644
--- a/src/com/android/settings/deviceinfo/PrivateVolumeUnmount.java
+++ b/src/com/android/settings/deviceinfo/PrivateVolumeUnmount.java
@@ -29,11 +29,11 @@
 import android.widget.TextView;
 
 import com.android.internal.logging.MetricsProto.MetricsEvent;
-import com.android.settings.InstrumentedFragment;
 import com.android.settings.R;
+import com.android.settings.SettingsPreferenceFragment;
 import com.android.settings.deviceinfo.StorageSettings.UnmountTask;
 
-public class PrivateVolumeUnmount extends InstrumentedFragment {
+public class PrivateVolumeUnmount extends SettingsPreferenceFragment {
     private VolumeInfo mVolume;
     private DiskInfo mDisk;