Fixing layout issue causing overlay to sometimes not appear.

- We were incorrectly making calls that could request layout after the
  view was detached from the parent, causing a messed up 
  layout-invalidation hierarchy path.  Now ensuring that we always reset
  the view before detaching, and after attaching.  As a result of this,
  we need to ensure that the same optimization as before applies, which 
  is that children of TaskView don’t affect the relayout of TaskView.
  We do so by making TaskView a subclass of FixedSizeFrameLayout which
  only takes layout updates uni-directionally down the view hierarchy.
- This CL also fixes an issue with missing task bar buttons due to an
  optimization which did not update the visibility and translation of
  buttons if a view is laid out after the task view size has changed.
- Removing double measurement of TaskView sub-children
- Removing unnecessary invalidate after marking the thumbnail as 
  invisible

Change-Id: If8a330733941add1f4214af792227345d6a26309