On WebOS 3.0 we've noticed an issue in production, where TVs are slowly
starting to throw the following error after a user has watched at least
30+ episodes: `Code: 6006 Category: 6 Severity: 2 ["EME v0.1b key
error",{"errorCode":{"code":1,"systemCode":65535}},"0xffff"]` and can
only be resolved by clearing the app cache, or unplugging the TV.
Further investigation revealed that current workflow, where MSE is
destroyed before DRM Engine causes that old EME implementation is not
able to close session properly.
We've tried to enable setting server certificates to optimize playback
start, but turned out that with our widevine certificate shaka was
throwing 6004 error. The issue is not reproducible starting from Tizen
5.5. The same certificate was working properly also on Chrome.
webOS platforms don't contain OS version explicitly in user agent,
instead they signal it via chrome version. This PR fixes webOS 4 & 5
methods and unifies all webOS check methods.