Suppress unchecked cast warnings in test

Change-Id: I8120473fc8fd1c4408c27394b84cd6b7f6dd14a7
diff --git a/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/DesugaredLibraryConfigurationParsingTest.java b/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/DesugaredLibraryConfigurationParsingTest.java
index 1141cb3..12ed820 100644
--- a/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/DesugaredLibraryConfigurationParsingTest.java
+++ b/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/DesugaredLibraryConfigurationParsingTest.java
@@ -299,9 +299,13 @@
     } else if (element instanceof Integer) {
       builder.append(element);
     } else if (element instanceof List) {
-      toJsonList((List<Object>) element, builder);
+      @SuppressWarnings("unchecked")
+      List<Object> elements = (List<Object>) element;
+      toJsonList(elements, builder);
     } else if (element instanceof Map) {
-      toJsonObject((Map<String, Object>) element, builder);
+      @SuppressWarnings("unchecked")
+      Map<String, Object> elements = (Map<String, Object>) element;
+      toJsonObject(elements, builder);
     } else {
       throw new IllegalStateException("Unexpected object type: " + element.getClass());
     }