Add SystemMonitor::GetAttachedMediaDevices().

BUG=none
TEST=included
Review URL: https://chromiumcodereview.appspot.com/10332190

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@138148 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed