WebSurface.InBackgroundMode

Enable/disable low-resource background mode, where javascript and repaint timers are throttled, resources are more aggressively purged from memory, and audio/video elements are paused. When background mode is enabled, all HTML5 video and audio objects will execute ".pause()" and gain the property "._steam_background_paused = 1". When background mode is disabled, any video or audio objects with that property will resume with ".play()".