Add test for MediaRouter2#getControllers

import static org.junit.Assert.assertFalse;

import static org.junit.Assert.assertNotEquals;

import static org.junit.Assert.assertNotNull;

import static org.junit.Assert.assertSame;

import static org.junit.Assert.assertTrue;

import static org.testng.Assert.assertThrows;

        assertFalse(systemController.isReleased());

    }

    @Test

    public void testControllers() {

        List<RoutingController> controllers = mRouter2.getControllers();

        assertNotNull(controllers);

        assertFalse(controllers.isEmpty());

        assertSame(mRouter2.getSystemController(), controllers.get(0));

    }

    // Helper for getting routes easily

    static Map<String, MediaRoute2Info> createRouteMap(List<MediaRoute2Info> routes) {

        Map<String, MediaRoute2Info> routeMap = new HashMap<>();