[EventEngine] Skip `dns_resolver_cooldown_test` for `event_engine_dns` experiment (#35251)

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Closes #35251

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35251 from yijiem:fix-dns-resolver-cooldown-test 857835200a
PiperOrigin-RevId: 589159895

src/core/lib/event_engine/posix_engine/posix_engine.cc

@@ -552,7 +552,7 @@ void PosixEventEngine::PosixDNSResolver::LookupTXT(LookupTXTCallback on_resolve,
 
 absl::StatusOr<std::unique_ptr<EventEngine::DNSResolver>>
 PosixEventEngine::GetDNSResolver(
-    const EventEngine::DNSResolver::ResolverOptions& options) {
+    GRPC_UNUSED const EventEngine::DNSResolver::ResolverOptions& options) {
 #ifndef GRPC_POSIX_SOCKET_RESOLVE_ADDRESS
   grpc_core::Crash("Unable to get DNS resolver for this platform.");
 #else  // GRPC_POSIX_SOCKET_RESOLVE_ADDRESS

src/core/lib/event_engine/posix_engine/posix_engine.h

@@ -198,7 +198,7 @@ class PosixEventEngine final : public PosixEventEngineWithFdSupport,
   bool CancelConnect(ConnectionHandle handle) override;
   bool IsWorkerThread() override;
   absl::StatusOr<std::unique_ptr<DNSResolver>> GetDNSResolver(
-      const DNSResolver::ResolverOptions& options) override;
+      GRPC_UNUSED const DNSResolver::ResolverOptions& options) override;
   void Run(Closure* closure) override;
   void Run(absl::AnyInvocable<void()> closure) override;
   // Caution!! The timer implementation cannot create any fds. See #20418.

test/core/client_channel/resolvers/dns_resolver_cooldown_test.cc

@@ -42,6 +42,7 @@
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/config/core_configuration.h"
 #include "src/core/lib/event_engine/default_event_engine.h"
+#include "src/core/lib/experiments/experiments.h"
 #include "src/core/lib/gprpp/debug_location.h"
 #include "src/core/lib/gprpp/no_destruct.h"
 #include "src/core/lib/gprpp/notification.h"
@@ -409,6 +410,14 @@ static void test_cooldown() {
 }
 
 TEST(DnsResolverCooldownTest, MainTest) {
+  // TODO(yijiem): This test tests the cooldown behavior of the PollingResolver
+  // interface. To do that, it overrides the grpc_dns_lookup_hostname_ares
+  // function and overrides the iomgr's g_dns_resolver system. We would need to
+  // rewrite this test for EventEngine using a custom EE DNSResolver or adding
+  // to the resolver_fuzzer.
+  if (grpc_core::IsEventEngineDnsEnabled()) {
+    GTEST_SKIP() << "Not with event engine dns";
+  }
   grpc_init();
 
   auto work_serializer = std::make_shared<grpc_core::WorkSerializer>(