AdbDebuggingManager: Add @Keep to mPublicKey.

This field is accessed via reflection, so make sure to not optimize
it out at compile-time.

Bug: 348040664
Test: Manual. Test adb wireless debugging (pairing/connect).
Flag: EXEMPT bugfix

Change-Id: I59befbe99cc7cf797eafc55a939692bfcb5abfef
1 file changed