Implement support for dumping session data to disk on all qualifying events. Open issues: Which events qualify? What events does CrashRestore currently support? Should we do incremental saves? Does the complexity of incremental saves outweigh the performance hit of dumping entire session each time?

The current implementation (328159) collects session data from various events, and saves to disk at timed intervals. The supported events are basically: - window open & close - tab add, remove, load, close, input & select - "browser:purge-session-history" notification WRT to incremental saves: This makes no sense in the context of the current implementation; Session data is incrementally stored in memory, and the disk i/o is flow-controlled by a timer. This bug, as initially written, is overly broad. If someone thinks there's another scenario important enough to bypass the timer, this bug should be used to track it. (Currently, the only event that bypasses the timer is "browser:purge-session-history", upon which we purge the file.) This bug is essentially fixed by the patch in 328159, and I'll resolve it once that patch lands.

This is implemented in the code that has been checked into both branch and trunk.