Add StarBorder and StarBorder.polygon, with example. (#108489)

dev/bots/analyze.dart

@@ -412,7 +412,7 @@ Future<void> verifyGoldenTags(String workingDirectory, { int minimumMatches = 20
     if (needsTag) {
       if (!hasTagNotation) {
         errors.add('${file.path}: Files containing golden tests must be tagged using '
-            '`@Tags(...)` at the top of the file before import statements.');
+            "@Tags(<String>['reduced-test-set']) at the top of the file before import statements.");
       } else if (!hasReducedTag) {
         errors.add('${file.path}: Files containing golden tests must be tagged with '
             "'reduced-test-set'.");

dev/bots/test/analyze_test.dart

@@ -74,10 +74,9 @@ void main() {
 
   test('analyze.dart - verifyGoldenTags', () async {
     final String result = await capture(() => verifyGoldenTags(testRootPath, minimumMatches: 6), exitCode: 1);
-    const String noTag = 'Files containing golden tests must be '
-        'tagged using `@Tags(...)` at the top of the file before import statements.';
-    const String missingTag = 'Files containing golden tests must be '
-        "tagged with 'reduced-test-set'.";
+    const String noTag = "Files containing golden tests must be tagged using @Tags(<String>['reduced-test-set']) "
+        'at the top of the file before import statements.';
+    const String missingTag = "Files containing golden tests must be tagged with 'reduced-test-set'.";
     String lines = <String>[
         'test/analyze-test-input/root/packages/foo/golden_missing_tag.dart: $missingTag',
         'test/analyze-test-input/root/packages/foo/golden_no_tag.dart: $noTag',

packages/flutter/lib/painting.dart

@@ -56,6 +56,7 @@ export 'src/painting/rounded_rectangle_border.dart';
 export 'src/painting/shader_warm_up.dart';
 export 'src/painting/shape_decoration.dart';
 export 'src/painting/stadium_border.dart';
+export 'src/painting/star_border.dart';
 export 'src/painting/strut_style.dart';
 export 'src/painting/text_painter.dart';
 export 'src/painting/text_span.dart';

packages/flutter/lib/src/material/slider.dart

@@ -144,7 +144,8 @@ class Slider extends StatefulWidget {
        assert(min != null),
        assert(max != null),
        assert(min <= max),
-       assert(value >= min && value <= max),
+       assert(value >= min && value <= max,
+         'Value $value is not between minimum $min and maximum $max'),
        assert(divisions == null || divisions > 0);
 
   /// Creates an adaptive [Slider] based on the target platform, following