improved usability of the scroll operation

When I scroll diagonally, it is determined whether you display utility buttons in a direction.

For example, I may scroll slightly diagonally when I let you scroll up and down. (easy to be generated when I operate it with one hand)
The angle that utility buttons is displayed by diagonal scroll when it is a current version is wide.
When it is the version of the pull request, an angle necessary for utility buttons to display it becomes narrow, and erroneous operation decreases.