Fix performance-for-range-copy warnings

Bug: 30413223
Test: make with WITH_TIDY=1 DEFAULT_GLOBAL_TIDY_CHECKS=-*,performance*
Change-Id: Ie481e88025a7a1f3abde8ff63420d5ccd8577e52
diff --git a/cmds/statsd/tests/anomaly/AnomalyTracker_test.cpp b/cmds/statsd/tests/anomaly/AnomalyTracker_test.cpp
index 218d52a..e125887 100644
--- a/cmds/statsd/tests/anomaly/AnomalyTracker_test.cpp
+++ b/cmds/statsd/tests/anomaly/AnomalyTracker_test.cpp
@@ -71,12 +71,12 @@
                          const std::shared_ptr<DimToValMap>& currentBucket,
                          const std::set<const MetricDimensionKey>& trueList,
                          const std::set<const MetricDimensionKey>& falseList) {
-    for (MetricDimensionKey key : trueList) {
+    for (const MetricDimensionKey& key : trueList) {
         if (!tracker.detectAnomaly(bucketNum, key, getBucketValue(currentBucket, key))) {
             return false;
         }
     }
-    for (MetricDimensionKey key : falseList) {
+    for (const MetricDimensionKey& key : falseList) {
         if (tracker.detectAnomaly(bucketNum, key, getBucketValue(currentBucket, key))) {
             return false;
         }