Allow customization of selection indicator

PiperOrigin-RevId: 589867180

components/BottomNavigation/src/MDCBottomNavigationBar.h

@@ -151,6 +151,35 @@ typedef NS_ENUM(NSInteger, MDCBottomNavigationBarAlignment) {
  */
 @property(nonatomic, strong, readwrite, nonnull) UIColor *selectedItemTitleColor;
 
+/**
+ If @c YES, a pill-shaped "active indicator" is used to show which item is currently selected. The
+ active indicator is centered around the selected icon, and animates in/out when a new item is
+ selected.
+
+ Note that using the active indicator turns off any ink/ripple behavior, as they should not both be
+ used as an indication of selection of a new item.
+
+ Defaults to @c NO.
+ */
+@property(nonatomic, assign) BOOL showsSelectionIndicator;
+
+/**
+ Size of the active indicator.
+
+ Only has an impact if @c useActiveIndicator is set to @c YES.
+
+ Defaults to 30, 60.
+ */
+@property(nonatomic, assign) CGSize selectionIndicatorSize;
+
+/**
+  Background color for the active indicator. Only has an impact if @c useActiveIndicator is set to
+  @c YES.
+
+  Defaults to #C3D9F2.
+ */
+@property(nonatomic, strong, nonnull) UIColor *selectionIndicatorColor;
+
 /**
  Color of unselected items. Applies color to items' icons. Text is not displayed in unselected mode.
  Default color is dark gray.

components/BottomNavigation/src/private/MDCBottomNavigationBar+Private.h

@@ -40,9 +40,4 @@
 
 @property(nonatomic, readonly) BOOL isTitleBelowIcon;
 
-// Selection indicator
-@property(nonatomic, assign) BOOL showsSelectionIndicator;
-@property(nonatomic, assign) CGSize selectionIndicatorSize;
-@property(nonatomic, strong, nonnull) UIColor *selectionIndicatorColor;
-
 @end