ButtonSystem requires some more work.
# Conflicts: # osu.Game/Graphics/UserInterface/OsuSliderBar.cs
# Conflicts: # osu.Game.Modes.Osu/Scoring/OsuScoreProcessor.cs
# Conflicts: # osu.Desktop.VisualTests/Tests/TestCaseResults.cs # osu.Game/Screens/Ranking/ResultModeButton.cs # osu.Game/Screens/Ranking/Results.cs