uGUI: Raycasters sorting doesn't match Canvas sorting (4.6.1p5)

# PROBLEM
When you have 2 Canvas with 'Screen Space - Overlay' render mode on same scene, set 'Sort Order' of one of the canvas to '-1' and leave the other as is ('0'). Now the canvas with sort order '-1' is visually displayed behind other canvas, but is the first one to receive clicks. Issue appears since version 4.6.1p2 of uGUI ( https://bitbucket.org/Unity-Technologies/ui/commits/7ac0f0d81f26c75250053db863a1b63bcf10c4bd?at=4.6 ) commit #7ac0f0d81f26c75250053db863a1b63bcf10c4bd , where EventSystem.RaycastComparer logic has been changed.

I assume that problem comes from the base value of sortOrderPriority and renderOrderPriority in BaseRaycaster. They should also be changed to int.MinValue (because lower value has higher priority).

# REPRODUCTION
Launch provided sample project and click on highlighted area.