No elevation or corner radius displayed for CardView that is inside a CoordinatorLayout

Question

I think this might be a bug, but will ask just here just in case...

I am using the Cheesesquare demo (synced to latest version this morning), I don't see elevation or radius for a CardView.

I think I can add the following attributes to the CardView, but it doesn't work:

card_view:cardUseCompatPadding="true"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="6dp"

(edit) - also added no transparency color, as per this SO:

card_view:cardBackgroundColor="#ffffff"

The complete CardView (for the "Info" card). I have tried (lines 73-99 of activity_detail.xml):

 <android.support.v7.widget.CardView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="@dimen/card_margin"
            card_view:cardUseCompatPadding="true"
            card_view:cardCornerRadius="4dp"
            card_view:cardElevation="6dp">

            <LinearLayout
                style="@style/Widget.CardContent"
                android:layout_width="match_parent"
                android:layout_height="wrap_content">

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="Info"
                    android:textAppearance="@style/TextAppearance.AppCompat.Title" />

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="@string/cheese_ipsum" />

            </LinearLayout>

        </android.support.v7.widget.CardView>

Is there anything else I need to do? I think this should display - but it is not - on any device.

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