UI: Infinite Video Scanning (after session gives up)

[hnryjms]

Right now, the video detect code will scan for a video 10 seconds, and then give up without reporting any status back to the background process (to then be reported to the popup UI). This is the case because right now, the port is not open until the video is detected, and Host.js treats any name: session port as a successful video discovery (which then will prompt the UI to move to the Ready state).

We need to either prevent the frame->background (SessionPort) from being assumed as a video discovery event, or we need to use some other notification system to show that no video has been detected. Preferably, we would wait until every frame is done scanning for a video.

We also should add logic that prevents multiple parallel scans for a video from occurring within a single frame/tab at once.