Move 'notifyFinishedSignal' into a separate function

To reduce the size of 'receiveFinishedSignals' and to simplify the
future CLs in this area, let's move the part where the Java code is
being notified into a separate function.

The behaviour should remain the same.

Test: atest InputEventSenderAndReceiverTest
Bug: 169866723
Change-Id: If0f0d630600a754d01d761f7a3bafce342b96d26
2 files changed