system_api: bluetooth: Add ConnectDevice method constant

This adds a constant for the ConnectDevice() method of Adapter
interface.

BUG=chromium:1140471
TEST=none

Change-Id: Ifd9a08c34c73750a6c05734c31df0c62e1b7c7a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2488106
Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
Reviewed-by: Alain Michaud <alainm@chromium.org>
Tested-by: Miao-chen Chou <mcchou@chromium.org>
Commit-Queue: Alain Michaud <alainm@chromium.org>
diff --git a/system_api/dbus/bluetooth/dbus-constants.h b/system_api/dbus/bluetooth/dbus-constants.h
index bfcaf06..06fce1d 100644
--- a/system_api/dbus/bluetooth/dbus-constants.h
+++ b/system_api/dbus/bluetooth/dbus-constants.h
@@ -51,6 +51,7 @@
 constexpr char kHandleSuspendDone[] = "HandleSuspendDone";
 constexpr char kGetSupportedCapabilities[] = "GetSupportedCapabilities";
 constexpr char kSetLongTermKeys[] = "SetLongTermKeys";
+constexpr char kConnectDevice[] = "ConnectDevice";
 
 // Bluetooth Adapter properties.
 constexpr char kAddressProperty[] = "Address";