IndexedDB: Added UMA stat to measure time to close backing store.

IndexedDB: Added UMA stat to measure time to close backing store.

Close can block on a background compaction, so log to reveal possible
performance issues.

BUG=502025
Committed: https://crrev.com/f2d78ae3ab737eccbc676142341951ae8dfdc963
Cr-Commit-Position: refs/heads/master@{#335163}

[cmumford, 2015-06-18 21:16:13]

cmumford@chromium.org changed reviewers:
+ dgrogan@chromium.org

[cmumford, 2015-06-18 21:16:14]

I think we'll get 99.99% (or some very large number) of the closes taking zero
msec, but those doing a background compaction will block. Not sure there's a
better way to handle this.

Will add a histograms.xml reviewer if it looks ok to dgrogan@

[dgrogan, 2015-06-18 22:15:58]

lgtm

https://codereview.chromium.org/1180803003/diff/1/content/browser/indexed_db/...
File content/browser/indexed_db/leveldb/leveldb_database.cc (right):

https://codereview.chromium.org/1180803003/diff/1/content/browser/indexed_db/...
content/browser/indexed_db/leveldb/leveldb_database.cc:87:
LevelDBDatabase::~LevelDBDatabase() {
Mainly for my edification:

Looks like this gets called when the ref count on an instance of
IndexedDBBackingStore drops to 0, is that right? Is there still a timer that
keeps the database open for 2 seconds?

[cmumford, 2015-06-18 22:20:13]

cmumford@chromium.org changed reviewers:
+ mpearson@chromium.org

[cmumford, 2015-06-18 22:20:14]

+mpearson for review of histograms.xml

https://codereview.chromium.org/1180803003/diff/1/content/browser/indexed_db/...
File content/browser/indexed_db/leveldb/leveldb_database.cc (right):

https://codereview.chromium.org/1180803003/diff/1/content/browser/indexed_db/...
content/browser/indexed_db/leveldb/leveldb_database.cc:87:
LevelDBDatabase::~LevelDBDatabase() {
On 2015/06/18 22:15:58, dgrogan wrote:
> Mainly for my edification:
> 
> Looks like this gets called when the ref count on an instance of
> IndexedDBBackingStore drops to 0, is that right? Is there still a timer that
> keeps the database open for 2 seconds?

Yes, timer is still in IndexedDBFactoryImpl::ReleaseBackingStore(). So when the
timer closes the backing store (and eventually the LevelDBDatabase) this
function will be executed.

[Mark P, 2015-06-18 22:42:26]

histograms.xml lgtm

[cmumford, 2015-06-18 22:44:55]

The CQ bit was checked by cmumford@chromium.org

[commit-bot: I haz the power, 2015-06-18 22:45:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1180803003/1

[commit-bot: I haz the power, 2015-06-18 23:53:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-18 23:54:16]

Patchset 1 (id:??) landed as
https://crrev.com/f2d78ae3ab737eccbc676142341951ae8dfdc963
Cr-Commit-Position: refs/heads/master@{#335163}