merge in nyc-mr1-release history after reset to nyc-mr1-dev
diff --git a/v7/mediarouter/src/android/support/v7/app/MediaRouteButton.java b/v7/mediarouter/src/android/support/v7/app/MediaRouteButton.java
index 20e83aa..25288c0 100644
--- a/v7/mediarouter/src/android/support/v7/app/MediaRouteButton.java
+++ b/v7/mediarouter/src/android/support/v7/app/MediaRouteButton.java
@@ -513,6 +513,9 @@
                     }
                 }
             }
+
+            setEnabled(mRouter.isRouteAvailable(mSelector,
+                    MediaRouter.AVAILABILITY_FLAG_IGNORE_DEFAULT_ROUTE));
         }
     }