Fix lifecycle bug in when calling positionTask

Sometimes the resumed activity from another stack gets positioned
BELOW the top activity of the current stack. We need to carry over
the mResumedActivity to make sure onPause is called on the moved
activity.

Bug: 28235047
Change-Id: I09e6b032cd8d0b00dc5fdd06bec68e53c25aae73
1 file changed