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

Review URL: https://codereview.chromium.org/188383004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255648 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255648
Update vdaunittest golden MD5 sums for libva-intel-driver-1.2.2.

Migrate changes from codereview.chromium.org/181433022.

BUG=344486
TEST=build and run the test on link

Review URL: https://codereview.chromium.org/176843019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255649 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255649