IndexedDB: Prevent terminated worker from hanging connections

IndexedDB: Prevent terminated worker from hanging connections

IndexedDB database connection shutdown is normally blocked on waiting
for transactions to finish. And transaction finishing requires an
abort/onAbort message round-trip to the back-end. When a Worker
context is stopped, the communication channel goes away before the
response comes back, so the transaction never finishes and the
database connection never closes.

Fix by explicitly closing the connection when the execution context is
stopped.

R=alecflett@chromium.org,dgrogan@chromium.org,cmumford@chromium.org
BUG=242115
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165179

[jsbell, 2014-01-15 18:58:19]

dgrogan@, alecflett@ - please take a look?

[dgrogan, 2014-01-15 22:53:52]

Alec, can you get this one since you and Josh talked about it the other day?

[alecflett, 2014-01-15 23:40:23]

lgtm with minor comments about comments.

Possibly still worth mentioning worker stop case, but you've basically
simplified the close handshake for all cases, not just workers.

https://codereview.chromium.org/138473004/diff/30001/Source/modules/indexeddb...
File Source/modules/indexeddb/IDBDatabase.cpp (right):

https://codereview.chromium.org/138473004/diff/30001/Source/modules/indexeddb...
Source/modules/indexeddb/IDBDatabase.cpp:412: // down. So in the case of context
stop, just close immediately.
The comment could be generalized here - I think something along the lines of "We
know the context is stopping, so we can proactively close the backend without
waiting for an onabort/onclose event from the backend."

meaning, there's no other "Normally" behavior now, right? since
IDBDatabase::stop is actually closing the backend unconditionally...

[jsbell, 2014-01-15 23:56:56]

https://codereview.chromium.org/138473004/diff/30001/Source/modules/indexeddb...
File Source/modules/indexeddb/IDBDatabase.cpp (right):

https://codereview.chromium.org/138473004/diff/30001/Source/modules/indexeddb...
Source/modules/indexeddb/IDBDatabase.cpp:412: // down. So in the case of context
stop, just close immediately.
On 2014/01/15 23:40:23, alecflett wrote:
>  there's no other "Normally" behavior now, right? since
> IDBDatabase::stop is actually closing the backend unconditionally...

By "Normally" I meant "on explicit close() or GC", i.e. not context shutdown.
But I see what you mean, the comment is implying knowledge of the history of the
code. I'll fix.

[commit-bot: I haz the power, 2014-01-16 00:01:34]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jsbell@chromium.org/138473004/120001

[commit-bot: I haz the power, 2014-01-16 02:17:06]

Change committed as 165179