Avoid allocation of large canvases on the web (#1557)

experimental/material_3_demo/lib/color_palettes_screen.dart

@@ -252,11 +252,13 @@ class ColorGroup extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return Card(
+    return RepaintBoundary(
+      child: Card(
         clipBehavior: Clip.antiAlias,
         child: Column(
           children: children,
         ),
+      ),
     );
   }
 }

experimental/material_3_demo/lib/component_screen.dart

@@ -1910,7 +1910,8 @@ class ComponentDecoration extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return Padding(
+    return RepaintBoundary(
+      child: Padding(
         padding: const EdgeInsets.symmetric(vertical: 10.0),
         child: Column(
           children: [
@@ -1927,7 +1928,8 @@ class ComponentDecoration extends StatelessWidget {
               ],
             ),
             ConstrainedBox(
-            constraints: const BoxConstraints.tightFor(width: widthConstraint),
+              constraints:
+                  const BoxConstraints.tightFor(width: widthConstraint),
               child: Card(
                 elevation: 0,
                 shape: RoundedRectangleBorder(
@@ -1944,6 +1946,7 @@ class ComponentDecoration extends StatelessWidget {
             ),
           ],
         ),
+      ),
     );
   }
 }