JoystickInputMapperTest: migrate to InputMapperUnitTest

Bug: 283812079
Test: atest frameworks/native/services/inputflinger/tests/JoystickInputMapper_test.cpp
Test: atest frameworks/native/services/inputflinger/tests/CursorInputMapper_test.cpp
Flag: TEST_ONLY
Change-Id: Ia270695bf49cf3453b4d3ad7c0276bc6b7e6a963
diff --git a/services/inputflinger/reader/include/InputDevice.h b/services/inputflinger/reader/include/InputDevice.h
index 3844fab..be95eff 100644
--- a/services/inputflinger/reader/include/InputDevice.h
+++ b/services/inputflinger/reader/include/InputDevice.h
@@ -72,7 +72,7 @@
     inline std::optional<std::string> getDeviceTypeAssociation() const {
         return mAssociatedDeviceType;
     }
-    inline std::optional<DisplayViewport> getAssociatedViewport() const {
+    inline virtual std::optional<DisplayViewport> getAssociatedViewport() const {
         return mAssociatedViewport;
     }
     inline bool hasMic() const { return mHasMic; }