IndexedDB: Limit LevelDB's max open files
https://bugs.webkit.org/show_bug.cgi?id=109993

Reviewed by Tony Chang.

LevelDB keeps up to 1000 (by default) data files open at a time to
avoid having to open() them. This has caused chromium to hit the
process-wide open file limit. This patch changes max_open_files to 20,
as that's the minimum permitted by LevelDB and we have no reason to
think that performance will suffer because of the extra open calls.

No new tests - a chromium browser test that tracks the open LevelDB
files is plausible but is blocked on http://crbug.com/177249/.

* platform/leveldb/LevelDBDatabase.cpp:
(WebCore::openDB):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143512 268f45cc-cd09-0410-ab3c-d52691b4dbfc