Deprecate `ThemeData.dialogBackgroundColor` in favor of `DialogThemeData.backgroundColor`

The ThemeData.dialogBackgroundColor parameter was deprecated in favor of the DialogThemeData.backgroundColor parameter.

The defaults for the Dialog and AlertDialog widgets can be overridden with a component-specific theme like DialogThemeData. Previously, the ThemeData.dialogBackgroundColor parameter was used to override the default dialog background color, which was made redundant by DialogThemeData.

The ThemeData.dialogBackgroundColor is deprecated in favor of a component-specific theme. Use DialogThemeData to override the default background color.

Replace ThemeData.dialogBackgroundColor with DialogThemeData.backgroundColor to override the default dialog background color.

Code before migration:

theme: ThemeData(
  dialogBackgroundColor: Colors.orange,
),

Code after migration:

theme: ThemeData(
  dialogTheme: const DialogThemeData(backgroundColor: Colors.orange),
),

Landed in version: 3.28.0-0.1.pre
In stable release: 3.29

API documentation:

• ThemeData.dialogBackgroundColor
• DialogThemeData.backgroundColor
• DialogThemeData
• Dialog
• AlertDialog

Relevant issues:

• Issue #91772

Relevant PRs:

• Deprecate ThemeData.dialogBackgroundColor in favor of DialogTheme.backgroundColor