[Swift] [iOS 14.5] - Incorrect playback state reported by requestMediaPlaybackState on website first launch

[Nishant Bhasin]

Created attachment 431098 [details]
Screen recording of simulator showing incorrect state reported by requestMediaPlaybackState

Hi, I work on Firefox iOS and wanted to try out the following code that allows us to request media playback state. However I always get media state as `playing` on first launch of website.

Steps to reproduce: 
- Open a media website (Ex. youtube, soundcloud) using WKWebView 
- When the website is fully loaded try to run the following code on the same website to get its media state 

Actual result:
- The code will always print playing on first launch even though nothing is playing

Expected result:
- The code should show paused or suspended as there is no media playing on those websites

```
webView.requestMediaPlaybackState({ state in
    switch state {
    case .none:
        print("TAB - none")
    case .paused:
        print("TAB - paused")
    case .playing:
        print("TAB - playing")
    case .suspended:
        print("TAB - suspended")
    @unknown default:
        fatalError()
    }
})
```

API Link: https://trac.webkit.org/browser/webkit/trunk/Source/WebKit/UIProcess/API/Cocoa/WKWebView.h#L377

[Radar WebKit Bug Importer]

<rdar://problem/79462265>