Request SupportFeatureProvider to provide a support tab.

Bug: 28139604

In dashboard container, if supportFeatureProvider is able to provide a
tab, we display it in tabbed layout. Otherwise, display just
DashboardSummary without changing UI.

Change-Id: Ib7601ac925e1315e6b0928d020fe2d09bd389cd7

src/com/android/settings/overlay/FeatureFactory.java

@@ -59,6 +59,8 @@ public abstract class FeatureFactory {
         return sFactory;
     }
 
+    public abstract SupportFeatureProvider getSupportFeatureProvider();
+
     public static final class FactoryNotFoundException extends RuntimeException {
         public FactoryNotFoundException(Throwable throwable) {
             super("Unable to create factory. Did you misconfigure Proguard?", throwable);