Exclude VideoCaptureManagerTest.StartDeviceAndGetDeviceFormatInUse on mac valgrind.

BUG=247601
TBR=benwells@chromium.org

Review URL: https://codereview.chromium.org/146673002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246840 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246840