Move placeholders to a dedicated namespace

osu.Game/Online/Placeholders/Placeholder.cs

@@ -0,0 +1,29 @@
+// 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.
+
+using System;
+using osu.Framework.Graphics;
+using osu.Game.Graphics.Containers;
+
+namespace osu.Game.Online.Placeholders
+{
+    public abstract class Placeholder : OsuTextFlowContainer, IEquatable<Placeholder>
+    {
+        protected const float TEXT_SIZE = 22;
+
+        protected Placeholder()
+            : base(cp => cp.Font = cp.Font.With(size: TEXT_SIZE))
+        {
+            Anchor = Anchor.Centre;
+            Origin = Anchor.Centre;
+            TextAnchor = Anchor.TopCentre;
+
+            Padding = new MarginPadding(20);
+
+            AutoSizeAxes = Axes.Y;
+            RelativeSizeAxes = Axes.X;
+        }
+
+        public virtual bool Equals(Placeholder other) => GetType() == other?.GetType();
+    }
+}