Let TMH detect webm files using opus and VP9 codecs

From what I understand VP9/Opus is the future of webm. This
patch will make sure such files are properly identified
in their long descriptions. It should also prevent TMH from
trying to play a VP9 file in a browser only supporting webm.

Bug: 60245
Change-Id: Icd368504d986821d4650347694c5b6705ceabe5d
Merge "Let TMH detect webm files using opus and VP9 codecs"