PrefixedVideoFullscreenApiAvailability

Starting in M132, this policy will be removed, along with the prefixed video-specific fullscreen APIs. Setting the policy to enabled will allow the prefixed video-specific fullscreen APIs (e.g. Video.webkitEnterFullscreen()) to be used from Javascript. Setting the policy to disabled will prevent the prefixed video-specific fullscreen APIs from being used in Javascript, leaving only the standard fullscreen APIs (e.g. Element.requestFullscreen()). Setting the policy to runtime-enabled will allow the PrefixedFullscreenVideo runtime enabled feature flag to determine whether the prefixed video-specific fullscreen APIs are available to websites. If the policy is unset, the behavior defaults to runtime-enabled. Note: this policy is a temporary solution to help transition away from webkit-prefixed fullscreen APIs. M131 is the last release which will have this policy.