TextTheme display4 issue

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  MyAppState createState() {
    return new MyAppState();
  }
}

class MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
            title: 'Flutter Demo',
            theme: ThemeData(
                    primarySwatch: Colors.blue,
            canvasColor: Colors.pinkAccent),
            home: HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: 3,
      child: Scaffold(
        appBar: AppBar(
          title: Text('TextTheme display 4 issue'),
          bottom: TabBar(
            isScrollable: true,
            tabs: [
              Tab(text: 'textTheme'),
              Tab(text: 'primaryTextTheme'),
              Tab(text: 'accentTextTheme'),
            ],
          ),
        ),
        body: _getBody(context),
      ),
    );
  }

  _getBody(BuildContext context) {
    return TabBarView(
      children: <Widget>[
        TextThemeTabView(
          title: "textTheme",
          textTheme: Theme.of(context).textTheme,
        ),
        TextThemeTabView(
          title: "primaryTextTheme",
          textTheme: Theme.of(context).primaryTextTheme,
        ),
        TextThemeTabView(
          title: "accentTextTheme",
          textTheme: Theme.of(context).accentTextTheme,
        ),
      ],
    );
  }
}

class TextThemeTabView extends StatelessWidget {
  final String title;
  final TextTheme textTheme;

  const TextThemeTabView({Key key, this.title, this.textTheme}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        Expanded(child: _buildList()),
      ],
    );
  }

  _buildList() => ListView(
    children: <Widget>[
      Text(
        "Display 4",
        style: textTheme.display4,
      ),
      Text(
        "Display 3",
        style: textTheme.display3,
      ),
      Text(
        "Display 2",
        style: textTheme.display2,
      ),
      Text(
        "Display 1",
        style: textTheme.display1,
      ),
      Text(
        "Headline",
        style: textTheme.headline,
      ),
      Text(
        "Title",
        style: textTheme.title,
      ),
      Text(
        "Subhead",
        style: textTheme.subhead,
      ),
      Text(
        "Body 2",
        style: textTheme.body2,
      ),
      Text(
        "Body 1",
        style: textTheme.body1,
      ),
      Text(
        "Caption",
        style: textTheme.caption,
      ),
      Text(
        "Button",
        style: textTheme.button,
      ),
    ],
  );
}