Update proguard config to keep base Preference class
Update proguard config to keep base Preference class

b/23419547

Change-Id: Id9963d0033a484a7cae8a08926ad972f90558abf

androidx/androidx,aosp-mirror/platform_frameworks_support,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,aosp-mirror/platform_frameworks_support,androidx/androidx,aosp-mirror/platform_frameworks_support,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,aosp-mirror/platform_frameworks_support,AndroidX/androidx,aosp-mirror/platform_frameworks_support,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx