Always clear callback after WaveOut Stop().

Always clear callback after WaveOut Stop().

If an error occurs after Stop() the callback may be destroyed, yet
the callback value was not cleared.  During Close() stop may be called
again, if an error occurs the free'd callback will be notified of the
error...

BUG=none
TEST=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243649

[DaleCurtis, 2014-01-07 01:44:54]

Found a few crashes while digging through reports.

[henrika (OOO until Aug 14), 2014-01-07 08:45:25]

Please forgive me if I am slow here but I am unable to see where your do what
the title says: "Always clear callback after WaveOut Stop()."

[DaleCurtis, 2014-01-07 18:34:55]

See line 280.  Previously the code could return early without clearing the
callback.

[DaleCurtis, 2014-01-07 18:54:41]

Err, line 272 now.  My first patch was completely wrong!  I misread the
UnregisterWaitEx documentation.  So long as you provide INVALID_HANDLE_VALUE the
function will automatically wait for callbacks and never return
ERROR_IO_PENDING:

http://msdn.microsoft.com/en-us/library/windows/desktop/ms686876.aspx

[henrika (OOO until Aug 14), 2014-01-08 08:51:18]

LGTM. Thanks Dale.

[commit-bot: I haz the power, 2014-01-08 18:40:27]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dalecurtis@chromium.org/115523010/50001

[commit-bot: I haz the power, 2014-01-08 21:36:34]

Change committed as 243649