Tag demo scrollable container

Now that CarUiRecyclerViews no longer default to being considered
scrollable containers, we need to explicitly tag the demo scrollable
container in RotaryPlayground.

Test: scroll in "scroll" tab of the demo app
Bug: 160922045
Change-Id: I22c7d8a6e975d3a5718637d4d65e371254f2ac7c
Merged-In: I22c7d8a6e975d3a5718637d4d65e371254f2ac7c
diff --git a/RotaryPlayground/res/layout/rotary_scroll.xml b/RotaryPlayground/res/layout/rotary_scroll.xml
index 4153ca1..843a380 100644
--- a/RotaryPlayground/res/layout/rotary_scroll.xml
+++ b/RotaryPlayground/res/layout/rotary_scroll.xml
@@ -26,11 +26,18 @@
         android:layout_height="wrap_content"
         android:singleLine="true"/>
 
+    <!-- Use contentDescription to enable rotary scrolling for this view. With rotary scrolling
+         enabled, rotation will scroll rather than moving the focus if moving the focus would
+         cause a lot of scrolling. Rotary scrolling should be enabled for scrolling views which
+         contain content which the user may want to see but can't interact with, either alone or
+         with interactive (focusable) content. -->
     <com.android.car.ui.recyclerview.CarUiRecyclerView
         android:id="@+id/rotary_scroll_view"
+        android:contentDescription="com.android.car.ui.utils.VERTICALLY_SCROLLABLE"
         android:layout_width="match_parent"
         android:layout_height="0dp"
         android:layout_weight="1"/>
+    <!-- TODO(b/171339427) Use app:rotaryScrollEnabled instead of contentDescription. -->
 
     <EditText
         android:layout_width="match_parent"