Clear mCurSender when mCurChannel is modified.

This fixed an issue where an InputEventSender might outlive
its usefulness and continue to be used well after it should
have been disposed or recreated.

Also improves the queue management somewhat.

Bug: 8493879
Change-Id: I7e0b6a3c43cbe72f8762991f5d36560feebd214b
1 file changed