device/bluetooth: Update GATT descriptor value D-Bus bindings.
This CL updates the Chrome D-Bus bindings and modifies the device/bluetooth
GATT Chrome OS code to use the new bindings defined in crbug.com/378182 for
descriptor value reads and writes.
BUG=
378182
TEST=device_unittests; manual tests using custom bluetoothd
Committed:
https://src.chromium.org/viewvc/chrome?view=rev&revision=275718