Fix backward compatibility with Flutter@master & beta

Author: daohoangson

packages/core/test/src/core_legacy_test.dart

@@ -59,14 +59,15 @@ void main() {
 
     testWidgets('tsb.build', (tester) async {
       const html = '<span class="build-op">Foo</span>';
+      const abcdef = Color(0x00abcdef);
       final buildOp = BuildOp(
         onTree: (_, tree) => tree.append(
           WidgetBit.block(
             tree,
             WidgetPlaceholder(
               builder: (context, child) {
                 final style = tree.tsb.build(context).style;
-                final colored = style.copyWith(color: const Color(0x00abcdef));
+                final colored = style.copyWith(color: abcdef);
                 return Text('hi', style: colored);
               },
             ),
@@ -83,7 +84,7 @@ void main() {
         ),
         useExplainer: false,
       );
-      expect(explained, contains('0x00abcdef'));
+      expect(explained, contains(abcdef.toString()));
     });
   });
 

packages/core/test/tag_li_test.dart

@@ -1000,14 +1000,16 @@ Future<void> main() async {
         '<ul style="color: #f00"><li>Foo</li></ul>',
         useExplainer: false,
       );
-      expect(disc, contains('Color(0xffff0000)'));
+      const red = Color(0xffff0000);
+      expect(disc, contains(red.toString()));
 
       final circle = await explain(
         tester,
         '<ul style="color: #0f0"><li>Foo</li></ul>',
         useExplainer: false,
       );
-      expect(circle, contains('Color(0xff00ff00)'));
+      const green = Color(0xff00ff00);
+      expect(circle, contains(green.toString()));
     });
   });
 }