transition_group.xml

<RelativeLayout
    android:id="@+id/playlist"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/cover"
    android:gravity="center_vertical"
    android:padding="@dimen/activity_vertical_margin"
    android:transitionGroup="true">
…

<LinearLayout
    android:id="@+id/controls"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:gravity="center_horizontal"
    android:transitionGroup="true"
    app:layout_marginBottomPercent="5%">
…