Request landscape orientation when going full screen

[mtsyh]

Task/Issue URL: #3250

Description

Steps to test this PR

• Open a YouTube video
• After playback starts, tap the full screen button
• Observe full screen playback in landscape mode rather than portrait

Notes

• Unfortunately, Android seems to have removed the onShowCustomView API
  which allowed the WebView to specify full screen orientation. In that case, we might want to force landscape, as in this PR, because our browser orientation seems to be locked in portrait.
• I left the code which allows the WebView to specify the orientation, in case someone had feedback on another way we could find the requested orientation. If there is no longer any way to do this on Android, we can remove this code and just set landscape in toggleFullScreen without piping through BrowserViewState.

UI changes

Before	After

[mtsyh]

The commented code here demonstrates what was possible with the previous API. Since there isn't currently a way to retrieve requestedOrientation from the WebView we default to SCREEN_ORIENTATION_LANDSCAPE.

[cmonfortep]

Sorry for the late response here. We are currently checking staled PRs, and we are closing this one as per our contributions guidelines, we only accept contributions for accepted issues and labeled as Help Wanted. Thanks