Mac AVFoundation: clean removal of device observers

Mac AVFoundation device monitor: clean removal of device observers

This CL fixes a crash happening when Chrome shuts down or a capture
device is removed from the system while there are observers observing
the "suspended" property of the AVCaptureDevice going out of scope --
basically leaving the observer observing a zombie.

For that, the CrAVFoundationSuspendObserver registers to observe both
"suspended" and "connected". In the case of "connected" received, it
can only mean disconnected, so both observers are removed. The |device|
pointer is passed to -addObserver:forKeyPath:options:context: as the
|context|, and is received then in the -observeValueForKeyPath:... .

CrAVFoundationSuspendObserver renamed to CrAVFoundationDeviceObserver.

BUG=288562, 348917
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=255648

[mcasas, 2014-03-06 10:55:46]

rsesek@ PTAL.
avi@ OWNERS stamp please.

[Robert Sesek, 2014-03-06 17:08:20]

https://codereview.chromium.org/188383004/diff/1/content/browser/device_monit...
File content/browser/device_monitor_mac.mm (right):

https://codereview.chromium.org/188383004/diff/1/content/browser/device_monit...
content/browser/device_monitor_mac.mm:331: if ([keyPath isEqual:@"connected"]) {
nit: you don't have braces around the other if, so why this one, or why not that
one?

https://codereview.chromium.org/188383004/diff/1/content/browser/device_monit...
content/browser/device_monitor_mac.mm:332: [self
stopObserving:(CrAVCaptureDevice*)context];
static_cast

[mcasas, 2014-03-06 17:21:58]

rsesek@ PTAL.

https://codereview.chromium.org/188383004/diff/1/content/browser/device_monit...
File content/browser/device_monitor_mac.mm (right):

https://codereview.chromium.org/188383004/diff/1/content/browser/device_monit...
content/browser/device_monitor_mac.mm:331: if ([keyPath isEqual:@"connected"]) {
On 2014/03/06 17:08:20, rsesek wrote:
> nit: you don't have braces around the other if, so why this one, or why not
that
> one?

Done.
Apologies, forgot them after removing debug traces.

https://codereview.chromium.org/188383004/diff/1/content/browser/device_monit...
content/browser/device_monitor_mac.mm:332: [self
stopObserving:(CrAVCaptureDevice*)context];
On 2014/03/06 17:08:20, rsesek wrote:
> static_cast

Done.

[Robert Sesek, 2014-03-06 17:40:27]

lgtm

[mcasas, 2014-03-07 07:05:47]

avi@ ping.

[Avi (use Gerrit), 2014-03-07 14:14:32]

lgtm

[mcasas, 2014-03-07 14:19:19]

The CQ bit was checked by mcasas@chromium.org

[commit-bot: I haz the power, 2014-03-07 14:20:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mcasas@chromium.org/188383004/120001

[commit-bot: I haz the power, 2014-03-07 14:22:35]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-07 14:22:36]

Try jobs failed on following builders: mac_chromium_rel

[mcasas, 2014-03-07 14:55:44]

The CQ bit was checked by mcasas@chromium.org

[commit-bot: I haz the power, 2014-03-07 14:57:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mcasas@chromium.org/188383004/120001

[commit-bot: I haz the power, 2014-03-07 17:24:16]

Change committed as 255648