Define empty callback in Context Hub AIDL VTS

Current implementation results in registering a nullptr.

Bug: 194285834
Test: Run VTS
Change-Id: I68c75011a377013e2ee02ef0fc088d78af896e09
diff --git a/contexthub/aidl/vts/VtsAidlHalContextHubTargetTest.cpp b/contexthub/aidl/vts/VtsAidlHalContextHubTargetTest.cpp
index 2b91b97..4b0d60f 100644
--- a/contexthub/aidl/vts/VtsAidlHalContextHubTargetTest.cpp
+++ b/contexthub/aidl/vts/VtsAidlHalContextHubTargetTest.cpp
@@ -82,10 +82,28 @@
     }
 }
 
+class EmptyContextHubCallback : public android::hardware::contexthub::BnContextHubCallback {
+  public:
+    Status handleNanoappInfo(const std::vector<NanoappInfo>& /* appInfo */) override {
+        return Status::ok();
+    }
+
+    Status handleContextHubMessage(const ContextHubMessage& /* msg */,
+                                   const std::vector<String16>& /* msgContentPerms */) override {
+        return Status::ok();
+    }
+
+    Status handleContextHubAsyncEvent(AsyncEventType /* evt */) override { return Status::ok(); }
+
+    Status handleTransactionResult(int32_t /* transactionId */, bool /* success */) override {
+        return Status::ok();
+    }
+};
+
 TEST_P(ContextHubAidl, TestRegisterCallback) {
     bool success;
-    ASSERT_TRUE(contextHub->registerCallback(getHubId(), new IContextHubCallbackDefault(), &success)
-                        .isOk());
+    sp<EmptyContextHubCallback> cb = sp<EmptyContextHubCallback>::make();
+    ASSERT_TRUE(contextHub->registerCallback(getHubId(), cb, &success).isOk());
     ASSERT_TRUE(success);
 }
 
@@ -263,8 +281,8 @@
     // In VTS, we only test that sending the values doesn't cause things to blow up - GTS tests
     // verify the expected E2E behavior in CHRE
     bool success;
-    ASSERT_TRUE(contextHub->registerCallback(getHubId(), new IContextHubCallbackDefault(), &success)
-                        .isOk());
+    sp<EmptyContextHubCallback> cb = sp<EmptyContextHubCallback>::make();
+    ASSERT_TRUE(contextHub->registerCallback(getHubId(), cb, &success).isOk());
     ASSERT_TRUE(success);
 
     ASSERT_TRUE(contextHub->onSettingChanged(setting, true /* enabled */).isOk());