Adapt test for video mime types in MapRecorderWin.spec.js

[chrismayer]

The tests for mime types in MapRecorderWin.spec.js seem to have a bit of room for optimization. As stated by @sronveaux in #406

I was just thinking whether the test on default Chrome media possibilities was really useful written as is... it is run whatever the browser which is used to run the tests and so doesn't always give the expected result... and even with Chrome, it is only relevant if using the correct version of the browser... (...) I'd personally write a test to see if at least one format was available on the browser instead of testing a fixed list but it's only a suggestion...

Please share your thoughts about this.