Test: parcel marshalling for user credentials page

Unit test to verify that the internal Credential that gets passed to
dialogs for removing said credential is actually a valid Parcelable
object, since it's hard to provoke a marshal/unmarshal in real-world
usage (but not impossible).

Bug: 22541933
Change-Id: I780ca2d7b01fc6081b9ea8b2810cfc97f0433a86

src/com/android/settings/UserCredentialsSettings.java

@@ -194,8 +194,8 @@ public class UserCredentialsSettings extends InstrumentedFragment implements OnI
         }
     }
 
-    private static class Credential implements Parcelable {
-        private static enum Type {
+    static class Credential implements Parcelable {
+        static enum Type {
             CA_CERTIFICATE (Credentials.CA_CERTIFICATE),
             USER_CERTIFICATE (Credentials.USER_CERTIFICATE),
             USER_PRIVATE_KEY (Credentials.USER_PRIVATE_KEY),