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

Test: lunch aosp_cf_x86_phone-userdebug && m
Change-Id: Id2ece4b2a6317998e1dd177e853848cc3956f39f

java/app.go

@@ -1863,6 +1863,7 @@ func (u *usesLibrary) deps(ctx android.BottomUpMutatorContext, hasFrameworkLibs
 				"org.apache.http.legacy",
 				"android.hidl.base-V1.0-java",
 				"android.hidl.manager-V1.0-java")
+			ctx.AddVariationDependencies(nil, usesLibTag, optionalUsesLibs...)
 		}
 	}
 }

java/testing.go

@@ -230,6 +230,22 @@ func GatherRequiredDepsForTest() string {
 			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{