add new sample: nine grid image (from https://stackoverflow.com/questions/48056304/how-to-display-9-png-format-of-a-picture-in-flutter)

Samples/UIWidgetsSamples_2019_4/Assets/StreamingAssets/button.png.meta

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Samples/UIWidgetsSamples_2019_4/Assets/WidgetsSample/NinegridImageSample.cs

+using System.Collections.Generic;
+using Unity.UIWidgets.engine;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using Color = Unity.UIWidgets.ui.Color;
+using Image = Unity.UIWidgets.widgets.Image;
+using ui_ = Unity.UIWidgets.widgets.ui_;
+
+namespace UIWidgetsSample {
+    public class NinegridImageSample : UIWidgetsPanel {
+        protected override void main() {
+            ui_.runApp(new NinegridWidgetApp());
+        }
+    }
+    
+    class NinegridWidgetApp : StatelessWidget
+    {
+        public override Widget build(BuildContext context)
+        {
+            return new WidgetsApp(
+                color: Color.white,
+                home: new NinegridWidget(),
+                pageRouteBuilder: (settings, builder) =>
+                    new PageRouteBuilder(
+                        settings: settings,
+                        pageBuilder: (Buildcontext, animation, secondaryAnimation) => builder(context)
+                    )
+            );
+        }
+    }
+
+    public class NinegridWidget : StatefulWidget {
+        public override State createState() {
+            return new NinegridWidgetState();
+        }
+    }
+
+    class NinegridWidgetState : State<NinegridWidget> {
+        public override Widget build(BuildContext context) {
+            return new Center(
+                child: new Column(
+                        children: new List<Widget>
+                        {
+                            Image.file(
+                                "button.png",
+                                height: 100,
+                                width: 350,
+                                centerSlice: Rect.fromLTRB(15, 15, 35, 35)
+                                ),
+                            Image.file(
+                                "button.png",
+                                height: 100,
+                                width: 350,
+                                fit: BoxFit.fill
+                                )
+                        }
+                    )
+                );
+        }
+    }
+}

Samples/UIWidgetsSamples_2019_4/Assets/WidgetsSample/NinegridImageSample.cs.meta

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