Move files to UI namespace

osu.Game/Graphics/Containers/ExpandingButtonContainer.cs

@@ -0,0 +1,21 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+namespace osu.Game.Graphics.Containers
+{
+    /// <summary>
+    /// An <see cref="ExpandingContainer"/> with a long hover expansion delay.
+    /// </summary>
+    /// <remarks>
+    /// Mostly used for buttons with explanatory labels, in which the label would display after a "long hover".
+    /// </remarks>
+    public class ExpandingButtonContainer : ExpandingContainer
+    {
+        protected ExpandingButtonContainer(float contractedWidth, float expandedWidth)
+            : base(contractedWidth, expandedWidth)
+        {
+        }
+
+        protected override double HoverExpansionDelay => 750;
+    }
+}