Cleanup.

examples/flutter_gallery/lib/demo/calculator/logic.dart

@@ -260,6 +260,7 @@ class CalcExpression {
       case ExpressionState.Result:
         return appendOperation(Operation.Subtraction);
     }
+    assert(state != null);
     return null;
   }
 

examples/flutter_gallery/lib/demo/grid_list_demo.dart

@@ -46,7 +46,7 @@ class GridDemoPhotoItem extends StatelessWidget {
   }
 
   final Photo photo;
-final GridDemoTileStyle tileStyle;
+  final GridDemoTileStyle tileStyle;
   final BannerTapCallback onBannerTap; // User taps on the photo's header or footer.
 
   void showPhoto(BuildContext context) {