use FgThread.class instead of UiThread.class for lock object

As is seen, UiThread/IoThread/DisplayThread/BackgroundThread
all use itself class for lock object. And for FgThread,
FgThread.class should be used for lock object

Test: null

Change-Id: I56e46fab33ff78d26b3e5197500764c763dba042
Signed-off-by: yangbingqian <yangbingqian@xiaomi.com>
1 file changed