Revert "Revert "Use D8 by default for android_test""

This reverts commit 4e445be558e5b41dd8ac279ed6d25c41a9f0cd7b.

Reason for revert: GtsExoPlayerTestCases now uses multidex.

Test: m + manual builds for test_suites_x86_64_coverage
Change-Id: I608b3b79137b216f546446e1c4f89f4542572581
Bug: 192032291
diff --git a/java/java_test.go b/java/java_test.go
index 4c93824..56a4248 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -723,9 +723,9 @@
 		t.Errorf("atestNoOptimize should not optimize APK")
 	}
 
-	atestDefault := ctx.ModuleForTests("atestDefault", "android_common").MaybeRule("r8")
+	atestDefault := ctx.ModuleForTests("atestDefault", "android_common").MaybeRule("d8")
 	if atestDefault.Output == nil {
-		t.Errorf("atestDefault should optimize APK")
+		t.Errorf("atestDefault should not optimize APK")
 	}
 }