fix DefaultTextStyle not notifying updates for some changes (#9416)

packages/flutter/lib/src/widgets/text.dart

@@ -108,7 +108,13 @@ class DefaultTextStyle extends InheritedWidget {
   }
 
   @override
-  bool updateShouldNotify(DefaultTextStyle old) => style != old.style;
+  bool updateShouldNotify(DefaultTextStyle old) {
+    return style != old.style ||
+        textAlign != old.textAlign ||
+        softWrap != old.softWrap ||
+        overflow != old.overflow ||
+        maxLines != old.maxLines;
+  }
 
   @override
   void debugFillDescription(List<String> description) {

packages/flutter/test/widgets/default_text_style_test.dart

@@ -0,0 +1,43 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/widgets.dart';
+
+void main() {
+  testWidgets('DefaultTextStyle changes propagate to Text', (WidgetTester tester) async {
+    const Text textWidget = const Text('Hello');
+    const TextStyle s1 = const TextStyle(
+      fontSize: 10.0,
+      fontWeight: FontWeight.w800,
+      height: 123.0,
+    );
+
+    await tester.pumpWidget(const DefaultTextStyle(
+      style: s1,
+      child: textWidget
+    ));
+
+    RichText text = tester.firstWidget(find.byType(RichText));
+    expect(text, isNotNull);
+    expect(text.text.style, s1);
+
+    await tester.pumpWidget(const DefaultTextStyle(
+      style: s1,
+      textAlign: TextAlign.justify,
+      softWrap: false,
+      overflow: TextOverflow.fade,
+      maxLines: 3,
+      child: textWidget
+    ));
+
+    text = tester.firstWidget(find.byType(RichText));
+    expect(text, isNotNull);
+    expect(text.text.style, s1);
+    expect(text.textAlign, TextAlign.justify);
+    expect(text.softWrap, false);
+    expect(text.overflow, TextOverflow.fade);
+    expect(text.maxLines, 3);
+  });
+}