The first parameter of adding idle timer is an unique identity to communicate between ConnectivityService and netd. Netd will notify the activity change using the identity, so it's fine to replace the legacy type with transport type since we should deprecate the usage of legacy type. Bug: 170598012 Test: atest FrameworksNetTests Change-Id: Ia00606539b86872cca9a92285bd940c8a720a033