Remove duplicated subclasses construction

Change-Id: Ib4a7cbdde6d814a193d8cdffb875119044c3b026
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxingCandidateAnalysis.java b/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxingCandidateAnalysis.java
index c0a7655..5f61f9b 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxingCandidateAnalysis.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxingCandidateAnalysis.java
@@ -73,15 +73,13 @@
     }
 
     List<DexProgramClass> subtypes = subtypingInfo.getSubclasses(clazz);
-    ImmutableSet.Builder<DexProgramClass> subEnumClassesBuilder = ImmutableSet.builder();
     for (DexProgramClass subEnum : subtypes) {
       if (!isSubEnumUnboxingCandidate(subEnum)) {
         return;
       }
-      subEnumClassesBuilder.add(subEnum);
     }
     enumToUnboxCandidates.addCandidate(
-        appView, clazz, subEnumClassesBuilder.build(), graphLensForPrimaryOptimizationPass);
+        appView, clazz, ImmutableSet.copyOf(subtypes), graphLensForPrimaryOptimizationPass);
   }
 
   @SuppressWarnings("ReferenceEquality")