Deprecate `ThemeData.indicatorColor` in favor of `TabBarThemeData.indicatorColor`

The ThemeData.indicatorColor parameter was deprecated in favor of the TabBarThemeData.indicatorColor parameter.

The defaults for the TabBar widget can be overridden with a component-specific theme like TabBarThemeData. Previously, the ThemeData.indicatorColor parameter was used to override the default tab bar indicator color in Material Design 2, which was made redundant by TabBarThemeData.

The ThemeData.indicatorColor is deprecated in favor of a component-specific theme. Use TabBarThemeData to override the default indicator color.

Replace ThemeData.indicatorColor with TabBarThemeData.indicatorColor to override the default tab bar indicator color when ThemeData.useMaterial3 flag is set to false.

Code before migration:

theme: ThemeData(
  indicatorColor: Colors.red,
  useMaterial3: false,
),

Code after migration:

theme: ThemeData(
  tabBarTheme: const TabBarThemeData(indicatorColor: Colors.red),
  useMaterial3: false,
),

Landed in version: 3.30.0-0.0.pre
In stable release: 3.32

API documentation:

• ThemeData.indicatorColor
• ThemeData.useMaterial3
• TabBarThemeData.indicatorColor
• TabBarThemeData
• TabBar

Relevant issues:

• Issue #91772

Relevant PRs:

• Deprecate ThemeData.indicatorColor in favor of TabBarThemeData.indicatorColor