Fix racing condition of mTouchExcludeRegion

Copy region from DisplayContent.mTouchExcludeRegion instead of
directly refer to the same object of DisplayContent, and able to
protect it by lock of self class, don't have to lock out mWindowMap
on every tap.

This fix is to avoid racing condition of mTouchExcludeRegion.

Change-Id: I7401968167c2e539b4da2afe71e3020038fbfcbf
Signed-off-by: tingna_sung <tingna_sung@htc.com>