Tracking bug for Chrome-side work to integrate a shared library with AGSA that allows us to trigger some UI (e.g. Sharebear prototype chathead UI) when we detect a screenshot is taken. This is just tracking the work to make that possible/build a prototype (we still need to flesh out the details of what the entrypoint UI will actually look like).

For reference, here's the bug where Pete added the screenshot detection code: Issue 857505. And here's the design doc: https://docs.google.com/document/d/1iyiVQODF1qh_Qiz7Is1y9jvWt1DYjgXmiJgLbFt2tSs/edit?usp=sharing.