Updating the Chip demo in the Gallery to include all the new types of chips. (#16522)

This chip demo is more interactive than the last one, trying to exercise all of the types of chips for a demo that lets you select different types of "chips" (like tortilla, wood, micro, etc.), and then filter them and select an action on them.

packages/flutter/lib/src/material/circle_avatar.dart

@@ -146,7 +146,7 @@ class CircleAvatar extends StatelessWidget {
   Widget build(BuildContext context) {
     assert(debugCheckHasMediaQuery(context));
     final ThemeData theme = Theme.of(context);
-    TextStyle textStyle = theme.primaryTextTheme.title.copyWith(color: foregroundColor);
+    TextStyle textStyle = theme.primaryTextTheme.subhead.copyWith(color: foregroundColor);
     Color effectiveBackgroundColor = backgroundColor;
     if (effectiveBackgroundColor == null) {
       switch (ThemeData.estimateBrightnessForColor(textStyle.color)) {

packages/flutter/lib/src/material/theme_data.dart

@@ -296,7 +296,7 @@ class ThemeData extends Diagnosticable {
        assert(iconTheme != null),
        assert(primaryIconTheme != null),
        assert(accentIconTheme != null),
-       assert(sliderTheme != null), 
+       assert(sliderTheme != null),
        assert(chipTheme != null),
        assert(platform != null);
 

packages/flutter/test/material/circle_avatar_test.dart

@@ -156,7 +156,7 @@ void main() {
       ),
     );
 
-    expect(tester.getSize(find.text('Z')), equals(const Size(20.0, 20.0)));
+    expect(tester.getSize(find.text('Z')), equals(const Size(16.0, 16.0)));
 
     await tester.pumpWidget(
       wrap(
@@ -185,7 +185,7 @@ void main() {
         ),
       ),
     );
-    expect(tester.getSize(find.text('Z')), equals(const Size(20.0, 20.0)));
+    expect(tester.getSize(find.text('Z')), equals(const Size(16.0, 16.0)));
   });
 
   testWidgets('CircleAvatar respects minRadius', (WidgetTester tester) async {