== Restoring sessions ==
TBDSR is designed for the following use cases:<br />1. Crash recovery without losing state;<br />2. Quit and restart from the same browsing position (either manually or automatically);<br />3. Upgrade Firefox or Extensions without losing state.<br /> For 1. and 3., we need to be able to resume in the exact same state, or users are going to be really annoyed – users can forgive a crash or an update if it just means that they lose the few seconds needed to restart Firefox, but not if they also lose their work. This means that we need to write all the costly stuff, including DOM Session Storage (which is currently what takes most of the disk space, iirc), forms, etc. Since crashes can happen at any time, we are pretty much in a dead-end here. For 2., since the user has quit and reopened manually, we can afford to save less (actually, we already do). We could probably remove closed tabs and windows. Now, while 2. is the least-commonly-used codepath (used only once per session), it can certainly be used to shrink the size of sessionstore.js for users who restart Firefox manually.
== Telemetry ==
