[EventEngine] Enable test-only WindowsEventEngine clients (#35546)

Closes #35546

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35546 from drfloob:win-ee-client-flip-202401 78abb9550b
PiperOrigin-RevId: 629747109

bazel/experiments.bzl

@@ -60,12 +60,16 @@ EXPERIMENTS = {
         },
         "off": {
             "core_end2end_test": [
+                "event_engine_client",
                 "promise_based_server_call",
             ],
             "endpoint_test": [
                 "tcp_frame_size_tuning",
                 "tcp_rcv_lowat",
             ],
+            "event_engine_client_test": [
+                "event_engine_client",
+            ],
             "flow_control_test": [
                 "multiping",
                 "peer_state_based_framing",

src/core/lib/event_engine/windows/windows_endpoint.cc

@@ -81,7 +81,7 @@ void WindowsEndpoint::AsyncIOState::DoTcpRead(SliceBuffer* buffer) {
   GRPC_EVENT_ENGINE_ENDPOINT_TRACE("WindowsEndpoint::%p reading", endpoint);
   if (socket->IsShutdown()) {
     socket->read_info()->SetErrorStatus(
-        absl::UnavailableError("Socket is shutting down."));
+        absl::InternalError("Socket is shutting down."));
     thread_pool->Run(&handle_read_event);
     return;
   }
@@ -131,7 +131,7 @@ bool WindowsEndpoint::Read(absl::AnyInvocable<void(absl::Status)> on_read,
                            SliceBuffer* buffer, const ReadArgs* /* args */) {
   if (io_state_->socket->IsShutdown()) {
     io_state_->thread_pool->Run([on_read = std::move(on_read)]() mutable {
-      on_read(absl::UnavailableError("Socket is shutting down."));
+      on_read(absl::InternalError("Socket is shutting down."));
     });
     return false;
   }
@@ -154,7 +154,7 @@ bool WindowsEndpoint::Write(absl::AnyInvocable<void(absl::Status)> on_writable,
   if (io_state_->socket->IsShutdown()) {
     io_state_->thread_pool->Run(
         [on_writable = std::move(on_writable)]() mutable {
-          on_writable(absl::UnavailableError("Socket is shutting down."));
+          on_writable(absl::InternalError("Socket is shutting down."));
         });
     return false;
   }
@@ -300,7 +300,7 @@ void WindowsEndpoint::HandleReadClosure::Run() {
       DumpSliceBuffer(buffer_, absl::StrFormat("WindowsEndpoint::%p READ",
                                                io_state->endpoint));
     }
-    status = absl::UnavailableError("End of TCP stream");
+    status = absl::InternalError("End of TCP stream");
     grpc_core::StatusSetInt(&status, grpc_core::StatusIntProperty::kRpcStatus,
                             GRPC_STATUS_UNAVAILABLE);
     buffer_->Swap(last_read_buffer_);

src/core/lib/experiments/rollouts.yaml

@@ -60,7 +60,7 @@
     posix: false
     # TODO(hork): resolve when the client end2end test flake rate reduces to
     # a tolerable amount.
-    windows: broken
+    windows: false
 - name: event_engine_dns
   default:
     # not tested on iOS at all