emoji_reaction test: Add another convenient test-setup check

Author: chrisbobbe

test/flutter_checks.dart

@@ -121,3 +121,8 @@ extension ElementChecks on Subject<Element> {
   Subject<Size?> get size => has((t) => t.size, 'size');
   // TODO more
 }
+
+extension MediaQueryDataChecks on Subject<MediaQueryData> {
+  Subject<TextScaler> get textScaler => has((x) => x.textScaler, 'textScaler');
+  // TODO more
+}

test/widgets/emoji_reaction_test.dart

@@ -127,6 +127,8 @@ void main() {
                 await setupChipsInBox(tester, reactions: reactions);
 
                 final reactionChipsList = tester.element(find.byType(ReactionChipsList));
+                check(MediaQuery.of(reactionChipsList))
+                  .textScaler.equals(TextScaler.linear(textScaleFactor));
                 check(Directionality.of(reactionChipsList)).equals(textDirection);
 
                 // TODO(upstream) Do these in an addTearDown, once we can: