Staff client memory leaks in 2.4

[Steven Chan]

We have been receiving field reports of what appears to be memory leaks in the
the 2.4 staff client causing it to slow down, emit error messages, and then crash.

One good report is from a library which had a crash of their circ workstation
about three hours before closing time. Their IT staff restarted it on a Windows
computer alongside the Task Manager in order to report on memory usage.

Time Memory Usage
5:56p XULRunner crashed, forced to quit Evergreen and reboot
5:57p 62,668K
7:44p 460,520K
8:42p 648,768K

Checking the database for that day and time period, we saw checkouts for only 14
unique patrons.

In order to isolate the problem further I used a straightforward test sequence
to measure memory leaks in the staff client as it performs checkouts, as
follows.

Test Setup:

* On a Windows XP running current production staff client, log into test
  server. The test server runs 2.4 and a snapshot of the production database.

* Press Ctl-t to show a 2nd tab and press F1 to show the patron barcode
  search form.

* Use a test patron account. Ensure that no alert message was entered in the
  patron account so that the checkout screen will show immediately apfter the
  patron search.

* Ensure that Autoprint is selected.
* Choose an item to check out.
* Use a 2nd workstation to check in the test item.

Test Sequence:

1. Search for test account.
2. Check out the test item.
3. Press Done and cancel the print attempt; the F1 search form is re-
displayed.
4. On 2nd workstation, check in the test item, so that it may be re-
used.

Repeat steps 1 to 4.

Using Task Manager, record the memory usage after step 3 and after it
stabilizes. With each checkout, the usage increases, never dropping to
the starting level.

A typical sequence of memory leak is (in MB) 17, 27, 25, 20, 22. If the
window is closed to leave only the login window active, memory usage
drops by only 4 MB. After 5 checkouts, we have a net increase of 107 MB
or about 20 MB per checkout.

The leak does not seem to depend on OS platform, Xulrunner version, or our fork
of software. Similar leaks are seen on Windows XP or Ubuntu 12.04; for
Xulrunner version 14, 21, 22, or 23; and on the official version of staff
client.

[Ben Shum (bshum)]

Since bug 1086458 still exists and is still open to further discussion and details, going to forward details from this to that bug (to keep all relevant history in one place) and then mark this as a duplicate.