[current_results] Fix two more lints

Change-Id: Ie2c4c4c2815ddbed98196b89aba97bb1327988ec
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/197222
Reviewed-by: William Hesse <whesse@google.com>
Commit-Queue: Karl Klose <karlklose@google.com>
diff --git a/current_results/lib/src/slice.dart b/current_results/lib/src/slice.dart
index 7e5e8ef..ac8e0be 100644
--- a/current_results/lib/src/slice.dart
+++ b/current_results/lib/src/slice.dart
@@ -136,8 +136,8 @@
         configurationSet.addAll(matchingConfigurations);
       }
     }
-    testPrefixes..sort();
-    for (int i = 0; i < testPrefixes.length; ++i) {
+    testPrefixes.sort();
+    for (var i = 0; i < testPrefixes.length; ++i) {
       while (i + 1 < testPrefixes.length &&
           testPrefixes[i + 1].startsWith(testPrefixes[i])) {
         testPrefixes.removeAt(i + 1);