Consider supporting an online "upgrade" experience when embedded in an IDE

In this scenario, I opened the Performance page in VS code when no debug sessions were available. This opened up the Performance screen for the "disconnected" state which allows the user to load offline data. I later ran a debug session, and still had the "offline" version of the Performance page.

It would be nice if a small banner popped up at the top of my performance tool that said something like
"A debug session is now available. Would you like to reload this tool and connect to it?". At that point the user could choose whether to ignore the message and continue looking at the offline data or reload the tool with the new app connection.

If the user chose to reload, DevTools could refresh itself so that the embedded IDE view would be reloaded. This would require the IDE to send an event to DevTools debug sessions change, and I think this event already exists because of the Flutter sidebar.

CC @DanTup @helin24

まず Performance ページの切断状態とオフラインデータ状態から始め、次に Flutter サイドバーに既存するデバッグセッション変更イベントをたどります。埋め込み IDE から、セッションが利用可能になったときに DevTools へ通知する方法と、ユーザーが制御する再読み込みの選択が現在のビューにどう影響すべきかを確認します。ユーザーが再読み込みを選択しない限りオフラインデータを破棄せずに遷移が処理されれば完了です。

索引モデルが issue の本文から書いたものです。