Spotify Web 1.63 - Notice on devices without Widevine, where playback can't work

Adds a notice at launch on devices without Widevine, such as some virtual phones and emulators. Spotify's web player needs Widevine to play music, so on those devices the player bar never starts and tapping a song does nothing. The Playback not supported notice explains this and points out that you can still browse and control your other devices through Spotify Connect.

It is the first popup at launch, ahead of the update dialog, because an app update can't add Widevine. Got it closes it. Nothing is stored, so it returns at every launch while Widevine is missing. Devices with Widevine never see it, and it stays hidden if the app can't tell whether Widevine is there. No setup is needed.

Widevine belongs to the device's system, not to the app or its WebView, so no WebView update can add it, including the app's own custom WebView. Google Play Services isn't needed for it either. An up-to-date WebView still matters on such a device, since it lets you log in, browse and control your other devices through Spotify Connect. So if the device's WebView is too old, the Update WebView popup still appears, and on a device without Widevine it now says that updating helps with login, browsing and Connect control but won't make the device play music itself. On devices with Widevine the popup is unchanged.

Limits: the notice only detects Widevine missing entirely. If it is present but not working, nothing is shown. It explains the problem but doesn't fix it. On the virtual phone where this was found (Android 7.1.2), playback transferred from another device gave a working player bar and controls, but choosing the virtual phone itself in Connect failed with "Try connecting to this device again later".