Mus Demo: Code cleanup in MusDemo::WindowTreeData

This CL performs the following cleanup:

* The logging of the time past since the last frame drawing is removed.
* The root_window_ and bitmap_window_ members are removed since they
  can be accessed from the window_tree_host_. Actually, only the bitmap
  window is now handled outside the initialization function and a
  helper function is added to retrieve it.
* The destructor is removed since the cleanup is done when members are
  destroyed: The bitmap window is owned by its parent itself owned by
  WindowTreeData::window_tree_host_ and WindowTreeData::timer_
  is stopped in base::Timer::~Timer().
* Add missing DISALLOW_COPY_AND_ASSIGN to WindowTreeData.
* Use proper coordinates for the bitmap window operations.


Cr-Commit-Position: refs/heads/master@{#450023}
1 file changed