Fixing page background not displayed when dragging from all apps

> Adding empty page synchronously, instead of waiting for a frame
> Changing launcher state from widgets screen in the same frame, similar to all apps
> Removing DragEnforcer, and moving that logic in side the workspace, disabled by a flag
> Using first page to get page bounds in drag layer, as last page may not have been measured

Change-Id: I172ba4e5ce44648ac55402d49994542c6e10f101