Ok, i didn't notice a little note they had at the bottom of the page
Note: If you are using the android-support-v7-mediarouter support library, you should note that it depends on the android-support-v7-appcompat library. In order for the v7 mediarouter library to compile, you must import both library projects into your development workspace. Then follow the procedure above to add the v7 appcompat project as a library to the v7 mediarouter library project.