Add support for client L2CAP sockets on Mac.

BUG=372495
TEST=BluetoothTest app
R=keybuk@chromium.org
TBR=tapted@chromium.org

Review URL: https://codereview.chromium.org/326313002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@277247 0039d316-1c4b-4281-b951-d872f2087c98

• apps/app_shim/chrome_main_app_mode_mac.mm[diff]
• base/mac/sdk_forward_declarations.h[diff]
• device/bluetooth/bluetooth.gyp[diff]
• device/bluetooth/bluetooth_l2cap_channel_mac.h[Added - diff]
• device/bluetooth/bluetooth_l2cap_channel_mac.mm[Added - diff]
• device/bluetooth/bluetooth_rfcomm_channel_mac.h[diff]
• device/bluetooth/bluetooth_rfcomm_channel_mac.mm[diff]
• device/bluetooth/bluetooth_socket_mac.mm[diff]