ConstClass Enums side-effect free

Change-Id: I582ddfafd76537e13b3ce98f0bf4b3c0b45f7c14
diff --git a/src/main/java/com/android/tools/r8/graph/DexItemFactory.java b/src/main/java/com/android/tools/r8/graph/DexItemFactory.java
index 8cb71bb..00a5cc3 100644
--- a/src/main/java/com/android/tools/r8/graph/DexItemFactory.java
+++ b/src/main/java/com/android/tools/r8/graph/DexItemFactory.java
@@ -625,7 +625,7 @@
 
   public Set<DexType> libraryTypesAssumedToBePresent =
       ImmutableSet.<DexType>builder()
-          .add(objectType, callableType, stringBufferType, stringBuilderType, stringType)
+          .add(objectType, callableType, stringBufferType, stringBuilderType, stringType, enumType)
           .addAll(primitiveToBoxed.values())
           .build();