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/reader/mapper/SingleTouchInputMapper.h b/services/inputflinger/reader/mapper/SingleTouchInputMapper.h
index f54c195..662e6bc 100644
--- a/services/inputflinger/reader/mapper/SingleTouchInputMapper.h
+++ b/services/inputflinger/reader/mapper/SingleTouchInputMapper.h
@@ -26,8 +26,8 @@
     explicit SingleTouchInputMapper(InputDeviceContext& deviceContext);
     ~SingleTouchInputMapper() override;
 
-    void reset(nsecs_t when) override;
-    void process(const RawEvent* rawEvent) override;
+    [[nodiscard]] std::list<NotifyArgs> reset(nsecs_t when) override;
+    [[nodiscard]] std::list<NotifyArgs> process(const RawEvent* rawEvent) override;
 
 protected:
     void syncTouch(nsecs_t when, RawState* outState) override;