modernize corners & borders in animation demo (#13352)

examples/flutter_gallery/lib/demo/animation/home.dart

@@ -216,12 +216,8 @@ class _AllSectionsLayout extends MultiChildLayoutDelegate {
       final Rect cardRect = _interpolateRect(columnCardRect, rowCardRect).shift(offset);
       final String cardId = 'card$index';
       if (hasChild(cardId)) {
-        // Add a small horizontal gap between the cards.
-        final Rect insetRect = new Rect.fromLTWH(
-          cardRect.left + 0.5, cardRect.top, cardRect.width - 1.0, cardRect.height
-        );
-        layoutChild(cardId, new BoxConstraints.tight(insetRect.size));
-        positionChild(cardId, insetRect.topLeft);
+        layoutChild(cardId, new BoxConstraints.tight(cardRect.size));
+        positionChild(cardId, cardRect.topLeft);
       }
 
       // Layout the title for index.
@@ -549,7 +545,7 @@ class _AnimationDemoHomeState extends State<AnimationDemoHome> {
     final double screenHeight = mediaQueryData.size.height;
     final double appBarMaxHeight = screenHeight - statusBarHeight;
 
-    // The scrolloffset that reveals the appBarMidHeight appbar.
+    // The scroll offset that reveals the appBarMidHeight appbar.
     final double appBarMidScrollOffset = statusBarHeight + appBarMaxHeight - _kAppBarMidHeight;
 
     return new SizedBox.expand(

examples/flutter_gallery/lib/demo/animation/widgets.dart

@@ -19,11 +19,8 @@ class SectionCard extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return new Padding(
-      padding: const EdgeInsets.only(bottom: 1.0),
-      child: new DecoratedBox(
+    return new DecoratedBox(
       decoration: new BoxDecoration(
-          borderRadius: new BorderRadius.circular(4.0),
         gradient: new LinearGradient(
           begin: Alignment.centerLeft,
           end: Alignment.centerRight,
@@ -40,7 +37,6 @@ class SectionCard extends StatelessWidget {
         colorBlendMode: BlendMode.modulate,
         fit: BoxFit.cover,
       ),
-      ),
     );
   }
 }