Centers affordance options when wide.

When the layout is wider than the number of option items, the option
items appeared start-aligned. This CL makes them center-aligned instead.

Fix: 267802884
Test: manually verified that the items are center-aligned in landscape
mode on a large screen devicew and scroll normally in portrait mode,
when they don't all fit on the screen

Change-Id: I3299981a33c7d4acfc9831e05d02e4acc81b5ad9
diff --git a/res/layout/fragment_lock_screen_quick_affordances.xml b/res/layout/fragment_lock_screen_quick_affordances.xml
index aba9a0c..36d1697 100644
--- a/res/layout/fragment_lock_screen_quick_affordances.xml
+++ b/res/layout/fragment_lock_screen_quick_affordances.xml
@@ -98,8 +98,9 @@
 
             <androidx.recyclerview.widget.RecyclerView
                 android:id="@id/affordances"
-                android:layout_width="match_parent"
+                android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
+                android:layout_gravity="center_horizontal"
                 android:clipToPadding="false"
                 android:paddingHorizontal="16dp"
                 android:clipChildren="false" />