[Media Router] Force DEFAULT cast mode when starting presentations from content.

chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js

Index: chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
diff --git a/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js b/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
index 43b695974823ce343588052f081016836645d57f..a980e49aef42806d286d31c8e83107f75865f2b1 100644
--- a/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
+++ b/chrome/test/data/webui/media_router/media_router_container_cast_mode_list_tests.js
@@ -58,6 +58,12 @@ cr.define('media_router_container_cast_mode_list', function() {
       var fakeCastModeListWithNonDefaultModesOnly = [];
 
       /**
+       * The list of CastModes to show with default mode forced.
+       * @type {!Array<!media_router.CastMode>}
+       */
+      var fakeCastModeListWithDefaultModeForced = [];
+
+      /**
        * The blocking issue to show.
        * @type {?media_router.Issue}
        */
@@ -92,6 +98,8 @@ cr.define('media_router_container_cast_mode_list', function() {
         fakeCastModeList = test_base.fakeCastModeList;
         fakeCastModeListWithNonDefaultModesOnly =
             test_base.fakeCastModeListWithNonDefaultModesOnly;
+        fakeCastModeListWithDefaultModeForced =
+            test_base.fakeCastModeListWithDefaultModeForced;
         fakeNonBlockingIssue = test_base.fakeNonBlockingIssue;
         fakeSinkList = test_base.fakeSinkList;
 
@@ -322,6 +330,20 @@ cr.define('media_router_container_cast_mode_list', function() {
         });
       });
 
+      // When a forced cast mode it set, it is used.
+      test('cast mode list respects forced mode', function(done) {
+        container.castModeList = fakeCastModeListWithDefaultModeForced;
+        MockInteractions.tap(container.$['container-header'].
+                             $['arrow-drop-icon']);
+        setTimeout(function() {
+          assertEquals(media_router.CastModeType.DEFAULT,
+                       container.shownCastModeValue_);
+          assertEquals('Cast google.com', container.headerText);
+          assertFalse(container.userHasSelectedCastMode_);
+          done();
+        });
+      });
+
       // Tests that the sink list does not contain any sinks that are not
       // compatible with the selected cast mode and are not associated with a
       // route.