[SQLite] Hack to touch page cache to debug slow connection close.

[SQLite] Hack to touch page cache to debug slow connection close.

The shutdown-monitor has noted cases where sqlite3_close() is taking a
very long time to finish.  In reviewing the code, writes are committed
before the close is called, so there should be almost no I/O involved
(excepting perhaps unlocking the file?).  One hypothesis is that the
SQLite page cache, which is LRU, may have very old pages which have
been paged out.  This change touches them all, so if they are paged
out the crash should move to this code.

BUG=95527
TEST=Monitor crash in bug, see if it changes.


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=101034

[Scott Hess - ex-Googler, 2011-09-13 23:15:17]

This is a little hacky, but we shouldn't retain it for long, right?

Putting it directly in the sqlite3.c/h files is only appropriate for debugging
purposes.  It should be safe enough, unless someone makes a change and
re-generates the file.  I'm actually fine with that, since we'll notice which
stacks we're getting.

The code should generally follow the routines in the stack trace on the bug.  A
bunch of those are just "Take a pointer, check something, cast it into something
else, and dig deeper", which is why I just have two functions.

[ramant (doing other things), 2011-09-14 01:06:34]

LGTM scott. thanks

[commit-bot: I haz the power, 2011-09-14 06:37:49]

Change committed as 101034