Add method to IFoo for testing NULL interfaces.

Bug: 32410513
Test: mma, hidl_test
Change-Id: I791c3a95e670a859e5e494ead987d2a93f5047a5
diff --git a/tests/foo/1.0/default/Foo.cpp b/tests/foo/1.0/default/Foo.cpp
index cf4f975..f7cc7c0 100644
--- a/tests/foo/1.0/default/Foo.cpp
+++ b/tests/foo/1.0/default/Foo.cpp
@@ -328,6 +328,12 @@
     return Void();
 }
 
+Return<void> Foo::echoNullInterface(const sp<IFooCallback> &cb, echoNullInterface_cb _hidl_cb) {
+    _hidl_cb(cb == nullptr, cb);
+
+    return Void();
+}
+
 IFoo* HIDL_FETCH_IFoo(const char* /* name */) {
     return new Foo();
 }