res:dock:: connect XMouseArea's CancelAllArea signal.

tower: https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/5f7dab1e693e4852afca293b8dd6997f/

Change-Id: I8f61154a1f0a1b52c9f74dc1a8c46cb9763ab58b