Add tests for detecting lost associated interfaces.

mojo/public/cpp/bindings/tests/associated_interface_unittest.cc

Index: mojo/public/cpp/bindings/tests/associated_interface_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/associated_interface_unittest.cc b/mojo/public/cpp/bindings/tests/associated_interface_unittest.cc
index e0a10b2ddbf99d7c208e9d2f75155c1bb6b87f2f..12482d1727d3c9070a942409f76f3211d236982f 100644
--- a/mojo/public/cpp/bindings/tests/associated_interface_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/associated_interface_unittest.cc
@@ -1122,6 +1122,29 @@ TEST_F(AssociatedInterfaceTest, BindLaterThreadSafeAssociatedInterfacePtr) {
   thread_safe_ptr = nullptr;
 }
 
+class DiscardingAssociatedPingProviderProvider
+    : public AssociatedPingProviderProvider {
+ public:
+  void GetPingProvider(
+      AssociatedPingProviderAssociatedRequest request) override {}
+};
+
+TEST_F(AssociatedInterfaceTest, CloseWithoutBindingAssociatedRequest) {
+  DiscardingAssociatedPingProviderProvider ping_provider_provider;
+  mojo::Binding<AssociatedPingProviderProvider> binding(
+      &ping_provider_provider);
+  auto provider_provider = binding.CreateInterfacePtrAndBind();
+  AssociatedPingProviderAssociatedPtr provider;
+  provider_provider->GetPingProvider(
+      mojo::MakeRequest(&provider, provider_provider.associated_group()));
+  PingServiceAssociatedPtr ping;
+  provider->GetPing(
+      mojo::MakeRequest(&ping, provider.associated_group()));
+  base::RunLoop run_loop;
+  ping.set_connection_error_handler(run_loop.QuitClosure());
+  run_loop.Run();
+}
+
 }  // namespace
 }  // namespace test
 }  // namespace mojo