I'm working on something similar. In chrome you can request an image of the active tab from a background page, write it to a canvas to downscale it, and then du

I'm working on something similar. In chrome you can request an image of the active tab from a background page, write it to a canvas to downscale it, and then dump it into indexeddb as a blob of base64. This only captures tabs that have been active at least once but I haven't noticed any additional latency using it.