Add android.test.base to class loader context for API version < 30.

Test: lunch aosp_cf_x86_phone-userdebug && m
Change-Id: Id2ece4b2a6317998e1dd177e853848cc3956f39f
diff --git a/java/testing.go b/java/testing.go
index 1967148..faf4d32 100644
--- a/java/testing.go
+++ b/java/testing.go
@@ -230,6 +230,22 @@
 			system_modules: "core-platform-api-stubs-system-modules",
 			installable: true,
 		}
+
+		java_library {
+			name: "android.test.base",
+			srcs: ["a.java"],
+			sdk_version: "none",
+			system_modules: "core-platform-api-stubs-system-modules",
+			installable: true,
+		}
+  
+		java_library {
+			name: "android.test.mock",
+			srcs: ["a.java"],
+			sdk_version: "none",
+			system_modules: "core-platform-api-stubs-system-modules",
+			installable: true,
+		}
 	`
 
 	systemModules := []string{