Simplifying workspace layout

Instead of creating workspace view larger than the screen size (so that it can be
zoomed out), restricting the size to the parent size and bypassing the drag events
directly to Workspace (since the workspace is smaller when zoomed out, it might not
qualify for all events otherwise).

Change-Id: I45e213dd6d16bec5feb6e7cf90bc6f7de4c6d305