991683 - [Session Restore] Don't [always] read sessionstore.js [early] during startup

Status: REOPENED

(Firefox :: Session Restore, defect)

Description

[David Teller [:Yoric] - still alive but not very active]

In many cases, we don't need to load the full sessionstore.js during startup:
1. in case of crash, if we just want to display about:sessionrestore, the list of windows and tab titles (and icons?) is sufficient – we could load the actual sessionstore.js later;
2. in case of not-crash, for users who do not restore the session automatically, we just need to know there is a session that may be restored.

I believe that we could therefore do the following:
- write a smaller file sessionoverview.js that contains only the data necessary for displaying the crash dialog;
- during startup, in case of crash, read sessionoverview.js before displaying the tab, sessionstore.js after;
- during startup, in case of not-crash, for users who do not restore the session automatically, read sessionstore.js after having displayed the welcome page;
- for users who restore automatically, still read sessionstore.js.

Comment 1

[Tim Taubert [:ttaubert] (inactive)]

(In reply to David Rajchenbach Teller [:Yoric] (please use "needinfo?") from comment #0)
> In many cases, we don't need to load the full sessionstore.js during startup:
> 1. in case of crash, if we just want to display about:sessionrestore, the
> list of windows and tab titles (and icons?) is sufficient – we could load
> the actual sessionstore.js later;

This sounds like a case that we really shouldn't optimize for.

> 2. in case of not-crash, for users who do not restore the session
> automatically, we just need to know there is a session that may be restored.

We are planning to enable session restore by default (bug 735914) that makes this an edge-case as well. I don't see that these two cases justify complicating existing and/or maintaining extra code.

Comment 2

[David Teller [:Yoric] - still alive but not very active]

Ah, I hadn't seen that part of bug 735914. Well, in that case...

Comment 3

[David Teller [:Yoric] - still alive but not very active]

Actually, I believe that we can still do this to optimize auto-restore. We'll want Telemetry first, though.

Comment 4

[David Teller [:Yoric] - still alive but not very active]

So, let's concentrate on clean shutdown and auto-restore.

1. During shutdown, write a smaller file (let's call it sessionoverview.js) that contains only the data necessary to create the tabs;
2. During startup, in case of not-crash auto-restore, read sessionoverview.js to create the tabs and populate the currently-focused tab;
3. Once sessionoverview.js is loaded, load the entire sessionstore.js and use the data to populate the other tabs lazily.