impl: Track CL 31043006 from upstream

https://codereview.chromium.org/31043006

It was a quite big rework in the DesktopRootWindowHost that needed many chan
in here. This commit also implements DesktopDragDropClientWayland, stubbing
its functionality for now.

Signed-off-by: Tiago Vignatti <tiago.vignatti@intel.com>

The patch was imported from https://github.com/tiagovignatti/ozone-wayland/
as of commit id 807e54ae6d4741c1c684c1bcad72b28292fe5370.

1)Fix namespace.
2)Minor cleanup.

Signed-off-by: Kalyan Kondapally <kalyan.kondapally@intel.com>
Unreviewed fix to get inputs working again.

Ensure DesktopRootWindowHostWayland is set as Dispatcher for
rootwindow.