Add visibility metrics to dialogs.

Bug: 30681529
Test: adb logcat -b events | egrep "(sysui_|notification_)"
Change-Id: I199d2e1b2cb8588a562b46bb8128d8ece24952f0
diff --git a/src/com/android/settings/UserCredentialsSettings.java b/src/com/android/settings/UserCredentialsSettings.java
index 8a75905..df073d1 100644
--- a/src/com/android/settings/UserCredentialsSettings.java
+++ b/src/com/android/settings/UserCredentialsSettings.java
@@ -50,6 +50,7 @@
 
 import com.android.internal.logging.MetricsProto.MetricsEvent;
 import com.android.internal.widget.LockPatternUtils;
+import com.android.settings.core.instrumentation.InstrumentedDialogFragment;
 import com.android.settingslib.RestrictedLockUtils;
 import com.android.settingslib.RestrictedLockUtils.EnforcedAdmin;
 
@@ -108,7 +109,7 @@
         }
     }
 
-    public static class CredentialDialogFragment extends DialogFragment {
+    public static class CredentialDialogFragment extends InstrumentedDialogFragment {
         private static final String TAG = "CredentialDialogFragment";
         private static final String ARG_CREDENTIAL = "credential";
 
@@ -166,6 +167,11 @@
             return builder.create();
         }
 
+        @Override
+        public int getMetricsCategory() {
+            return MetricsEvent.DIALOG_USER_CREDENTIAL;
+        }
+
         /**
          * Deletes all certificates and keys under a given alias.
          *