Make ImageRenderer clip its contents

Ooui.Forms/Renderers/ImageRenderer.cs

@@ -28,6 +28,7 @@ namespace Ooui.Forms.Renderers
             if (Control == null) {
                 var imageView = new Ooui.Image ();
                 SetNativeControl (imageView);
+                this.Style.Overflow = "hidden";
             }
 
             if (e.NewElement != null) {

Ooui/Style.cs

@@ -253,6 +253,11 @@ namespace Ooui
             set => this["order"] = value;
         }
 
+        public Value Overflow {
+            get => this["overflow"];
+            set => this["overflow"] = value;
+        }
+
         public Value PaddingTop {
             get => this["padding-top"];
             set => this["padding-top"] = value;