Repository: flutter
Issue: Text does not conform to DefaultTextStyle which is beyond Card
Labels: framework,f: material design,a: typography,has reproducible steps,P2,found in release: 2.5,found in release: 2.6,team-design,triaged-design

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## Steps to Reproduce

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I'm using DefaultTextStyle to set default TextStyle to all Text inside a Card. Widget tree:
- DefaultTextStyle -> Card -> Text : not work
- Card -> DefaultTextStyle -> Text : work
```dart
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: FooPage(),
    );
  }
}

class FooPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => FooPageState();
}

class FooPageState extends State<FooPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: new Text("Demo")),
      body: Column(
        children: <Widget>[
          DefaultTextStyle(
            style: TextStyle(fontSize: 30.0, color: Colors.blue),
            child: Card(
              child: Text('DefaultTextStyle outside Card does not work'),
            ),
          ),
          Card(
            child: DefaultTextStyle(
              style: TextStyle(fontSize: 30.0, color: Colors.blue),
              child: Text('DefaultTextStyle inside Card works'),
            ),
          ),
        ],
      ),
    );
  }
}
```

## Logs

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```
[✓] Flutter (Channel dev, v0.5.0, on Mac OS X 10.13.4 17E202, locale en-US)
    • Flutter version 0.5.0 at /Users/rain/flutter
    • Framework revision a863817c04 (4 days ago), 2018-05-26 12:29:21 -0700
    • Engine revision 2b1f3dbe25
    • Dart version 2.0.0-dev.58.0.flutter-97b6c2e09d

[✓] Android toolchain - develop for Android devices (Android SDK 27.0.3)
    • Android SDK at /Users/rain/Library/Android/sdk
    • Android NDK at /Users/rain/Library/Android/sdk/ndk-bundle
    • Platform android-27, build-tools 27.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b01)
    • All Android licenses accepted.

[✓] iOS toolchain - develop for iOS devices (Xcode 9.3.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 9.3.1, Build version 9E501
    • ios-deploy 1.9.2
    • CocoaPods version 1.5.2

[✓] Android Studio (version 3.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 24.2.1
    • Dart plugin version 173.4700
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b01)

[✓] VS Code (version 1.23.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Dart Code extension version 2.12.1
```