Replace duplicate with onWindowInfosChanged

The call to onWindowInfosChanged already creates new objects, so we
don't need to be extra careful when sending the window handles to the
dispatcher.

In this CL, use onWindowInfosChanged instead of having to explicitly
duplicate the handles.

Bug: 211379801
Test: TEST=inputflinger_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST
Change-Id: Ic25c7662592b3c0b7160f4e5c4f434358711e1f4