Sort timestamps in the same stream

Bug: 193166997
Test: TH
Change-Id: I3d48d4f0d0cad0cc9d44d1669925c3a7d16be094
diff --git a/hostsidetests/statsdatom/src/android/cts/statsdatom/lib/ReportUtils.java b/hostsidetests/statsdatom/src/android/cts/statsdatom/lib/ReportUtils.java
index d41337b..88f583f 100644
--- a/hostsidetests/statsdatom/src/android/cts/statsdatom/lib/ReportUtils.java
+++ b/hostsidetests/statsdatom/src/android/cts/statsdatom/lib/ReportUtils.java
@@ -150,8 +150,9 @@
                 atomTimestamp.add(Pair.create(atomInfo.getAtom(), timestampNs));
             }
         }
-        atomTimestamp.sort(Comparator.comparing(o -> o.second));
-        return atomTimestamp.stream().map(p -> p.first).collect(Collectors.toList());
+        return atomTimestamp.stream()
+                .sorted(Comparator.comparing(o -> o.second))
+                .map(p -> p.first).collect(Collectors.toList());
     }
 
     /**