Fix failing test

Author: elliette

packages/devtools_app/lib/src/shared/console/widgets/description.dart

@@ -303,6 +303,10 @@ class DiagnosticsNodeDescription extends StatelessWidget {
         // provide some contrast between the name and description if both are
         // present.
         textStyle = textStyle.merge(theme.subtleTextStyle);
+        final fontSize = textStyle.fontSize;
+        if (fontSize != null) {
+          textStyle = textStyle.copyWith(fontSize: fontSize);
+        }
       }
 
       if (diagnosticLocal.isCreatedByLocalProject) {
@@ -398,7 +402,11 @@ class DiagnosticsNodeDescription extends StatelessWidget {
       // those that were:
       if (!diagnosticLocal.isCreatedByLocalProject &&
           diagnosticLocal.description != '[root]') {
+        final fontSize = textStyle.fontSize;
         textStyle = textStyle.merge(theme.subtleTextStyle);
+        if (fontSize != null) {
+          textStyle = textStyle.copyWith(fontSize: fontSize);
+        }
       }
 
       var diagnosticDescription = buildDescription(