Take screenshots of pausing activity

Previous CL to optimize out excessive screenshots (ag/379669) was too
effective and didn't take screenshots when going into an activity
that had attribute Window_windowNoDisplay. Adding in the test for
ActivityRecord.noDisplay allows screenshots for this situation.

Fixes bug 13410507.

Change-Id: Ieafebf44b7d1a3ba18115e762fba113f8d1c0252