Merge changes Ibec23fdb,Id7be5129,I25af8fad,Idbabfe39,I86b10805, ... into nyc-dev

* changes:
  Hiding clear-all button on drag start.
  Adding hint text for drop targets.
  Fixing animation spec animation problem.
  Making the dismiss animation feel smoother.
  Fixing issue with gap between task views.
  Adding desired undocking animation.