Apply media padding in Gallery Pesto demo (#13668)

Applies horizontal safe area insets to the Pesto demo in the Gallery.
This is to support the iPhone X sensor housing notch and other similarly
creative display features when in landscape orientation.

examples/flutter_gallery/lib/demo/pesto_demo.dart

@@ -137,7 +137,13 @@ class _RecipeGridPageState extends State<RecipeGridPage> {
   }
 
   Widget _buildBody(BuildContext context, double statusBarHeight) {
-    final EdgeInsets padding = const EdgeInsets.all(8.0);
+    final EdgeInsets mediaPadding = MediaQuery.of(context).padding;
+    final EdgeInsets padding = new EdgeInsets.only(
+      top: 8.0,
+      left: 8.0 + mediaPadding.left,
+      right: 8.0 + mediaPadding.right,
+      bottom: 8.0
+    );
     return new SliverPadding(
       padding: padding,
       sliver: new SliverGrid(
@@ -432,6 +438,9 @@ class RecipeSheet extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return new Material(
+      child: new SafeArea(
+        top: false,
+        bottom: false,
         child: new Padding(
           padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 40.0),
           child: new Table(
@@ -497,6 +506,7 @@ class RecipeSheet extends StatelessWidget {
             )),
           ),
         ),
+      ),
     );
   }