Fix config change layout. (Part 2)

- Fixing issue where the initial state was not correct after rotating
  the screen.  We needed to update the layout, but that could only be 
  done after the task stack view is laid out.  Now we set a flag to 
  update the initial state of the layout on configuration change, and 
  only scrolling to the front when it makes sense.

Change-Id: I2586b90d1e869708b97bcd1a4446f4d87fa521cc