Fix errorprone warnings that should be errors am: 083e4f4123

Original change: https://android-review.googlesource.com/c/platform/external/mobile-data-download/+/2256435

Change-Id: I8c8fc141fb299820d048f622f812110afd1b09d1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/Android.bp b/Android.bp
index 36706ac..997ec78 100644
--- a/Android.bp
+++ b/Android.bp
@@ -78,4 +78,9 @@
     visibility: [
         "//packages/modules/AdServices:__subpackages__",
     ],
+    errorprone: {
+        javacflags: [
+            "-Xep:NoCanIgnoreReturnValueOnClasses:WARN",
+        ],
+    },
 }
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