Throw IAE when updating dynamic routes with none selected

A RoutingSessionInfo must have at least one selected class. Rather than
ignoring the call to notifyDynamicRoutesChanged(), this throws an
IllegalArgumentException, which is more visible and enforces the
requirement stated in the javadoc.

Test: Use sample app
Bug: 221284469
Bug: 205124386
Change-Id: I86ecda6f3ce32def8898f056a0a04b57224ae981

diff --git a/mediarouter/mediarouter/src/main/java/androidx/mediarouter/media/MediaRouteProvider.java b/mediarouter/mediarouter/src/main/java/androidx/mediarouter/media/MediaRouteProvider.java
index ed033e1..34f191f 100644
--- a/mediarouter/mediarouter/src/main/java/androidx/mediarouter/media/MediaRouteProvider.java
+++ b/mediarouter/mediarouter/src/main/java/androidx/mediarouter/media/MediaRouteProvider.java

@@ -602,6 +602,10 @@
          *                   the route controller.
          * @param dynamicRoutes The dynamic route descriptors for published routes.
          *                      At least a selected or selecting route should be included.
+         *
+         * @throws IllegalArgumentException Thrown when no dynamic route descriptors are {@link
+         * DynamicRouteDescriptor#SELECTED SELECTED} or {@link DynamicRouteDescriptor#SELECTING
+         * SELECTING}.
          */
         public final void notifyDynamicRoutesChanged(
                 @NonNull MediaRouteDescriptor groupRoute,
@@ -612,6 +616,23 @@
             if (dynamicRoutes == null) {
                 throw new NullPointerException("dynamicRoutes must not be null");
             }
+
+            boolean hasSelectedRoute = false;
+            for (DynamicRouteDescriptor route: dynamicRoutes) {
+                int state = route.getSelectionState();
+                if (state == DynamicRouteDescriptor.SELECTED
+                        || state == DynamicRouteDescriptor.SELECTING) {
+                    hasSelectedRoute = true;
+                    break;
+                }
+            }
+
+            if (!hasSelectedRoute) {
+                throw new IllegalArgumentException("dynamicRoutes must have at least one selected"
+                        + " or selecting route.");
+
+            }
+
             synchronized (mLock) {
                 if (mExecutor != null) {
                     final OnDynamicRoutesChangedListener listener = mListener;