Return events from mappers and InputDevice

We are changing the way android input events are reported from the
InputReader. Previously, the process was opaque - anywhere in the code
you were allowed to grab the listener and send events to it. Now, the
flow changes - you will have to explicitly return the events back to the
caller.

With the new approach, InputReader will ultimately be the one
dispatching the events to the listener.

Bug: 211379801
Test: atest inputflinger_tests
Change-Id: I2318ad1220fa66b197ca2a49b8625afcfb45103f
diff --git a/services/inputflinger/include/NotifyArgs.h b/services/inputflinger/include/NotifyArgs.h
index 611b1aa..f28dbf3 100644
--- a/services/inputflinger/include/NotifyArgs.h
+++ b/services/inputflinger/include/NotifyArgs.h
@@ -213,4 +213,6 @@
                                 NotifySensorArgs, NotifySwitchArgs, NotifyDeviceResetArgs,
                                 NotifyPointerCaptureChangedArgs, NotifyVibratorStateArgs>;
 
+const char* toString(const NotifyArgs& args);
+
 } // namespace android