Component theme normalization

CardTheme, DialogTheme and TabBarTheme were refactored to conform to Flutter's conventions for component themes. CardThemeData, DialogThemeData, and TabBarThemeData were added to define overrides for the defaults of the component visual properties. Releases of Flutter continue to normalize component themes like these for a more consistent theming experience in the material library.

In ThemeData:

• The type of the cardTheme property has been changed from CardTheme to CardThemeData.
• The type of the dialogTheme property has been changed from the DialogTheme to DialogThemeData.
• The type of tabBarTheme property has been changed from TabBarTheme to TabBarThemeData.

The return type of the component theme xTheme.of() methods and Theme.of().xTheme have also changed to xThemeData accordingly.

Code before migration:

final CardTheme cardTheme = Theme.of(context).cardTheme;
final CardTheme cardTheme = CardTheme.of(context);
​
final DialogTheme dialogTheme = Theme.of(context).dialogTheme;
final DialogTheme dialogTheme = DialogTheme.of(context);
​
final TabBarTheme tabBarTheme = Theme.of(context).tabBarTheme;
final TabBarTheme tabBarTheme = TabBarTheme.of(context);

Code after migration:

final CardThemeData cardTheme = Theme.of(context).cardTheme;
final CardThemeData cardTheme = CardTheme.of(context);
​
final DialogThemeData dialogTheme = Theme.of(context).dialogTheme;
final DialogThemeData dialogTheme = DialogTheme.of(context);
​
final TabBarThemeData tabBarTheme = Theme.of(context).tabBarTheme;
final TabBarThemeData tabBarTheme = TabBarTheme.of(context);

Landed in version: 3.27.0-0.0.pre
Stable release: 3.27

API documentation:

• ThemeData
• CardTheme
• DialogTheme
• TabBarTheme

Relevant PRs:

• Normalize ThemeData.cardTheme
• Normalize ThemeData.dialogTheme
• Normalize ThemeData.tabBarTheme