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/app.go b/java/app.go
index 768d9e9..8c5933a 100755
--- a/java/app.go
+++ b/java/app.go
@@ -1017,7 +1017,7 @@
 func AndroidTestFactory() android.Module {
 	module := &AndroidTest{}
 
-	module.Module.dexProperties.Optimize.EnabledByDefault = true
+	module.Module.dexProperties.Optimize.EnabledByDefault = false
 
 	module.Module.properties.Instrument = true
 	module.Module.properties.Supports_static_instrumentation = true
@@ -1071,6 +1071,7 @@
 func AndroidTestHelperAppFactory() android.Module {
 	module := &AndroidTestHelperApp{}
 
+	// TODO(b/192032291): Disable by default after auditing downstream usage.
 	module.Module.dexProperties.Optimize.EnabledByDefault = true
 
 	module.Module.properties.Installable = proptools.BoolPtr(true)
diff --git a/java/dex.go b/java/dex.go
index 13d6e4a..c943938 100644
--- a/java/dex.go
+++ b/java/dex.go
@@ -36,8 +36,8 @@
 	Main_dex_rules []string `android:"path"`
 
 	Optimize struct {
-		// If false, disable all optimization.  Defaults to true for android_app and android_test
-		// modules, false for java_library and java_test modules.
+		// If false, disable all optimization.  Defaults to true for android_app and
+		// android_test_helper_app modules, false for android_test, java_library, and java_test modules.
 		Enabled *bool
 		// True if the module containing this has it set by default.
 		EnabledByDefault bool `blueprint:"mutated"`
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")
 	}
 }