Added titles, changed done() overload to add_cleanup() call, changed timeout to explicit_timeout, and changed mp4 & webm order so MP4 is used if it is supported. 
diff --git a/media-source/mediasource-config-change-mp4-v-framerate.html b/media-source/mediasource-config-change-mp4-v-framerate.html index f4a6fe4..65266c4 100644 --- a/media-source/mediasource-config-change-mp4-v-framerate.html +++ b/media-source/mediasource-config-change-mp4-v-framerate.html 
@@ -1,6 +1,7 @@  <!DOCTYPE html>  <html>  <head> + <title>MP4 video-only frame rate change.</title>  <script src="/resources/testharness.js"></script>  <script src="/resources/testharnessreport.js"></script>  <script src="mediasource-util.js"></script>