Make the poll override function assert on non-zero timeout if invoked

from the end2end test thread itself (done by adding a TLS on that thread)

Also clang-format

test/cpp/end2end/async_end2end_test.cc

@@ -43,6 +43,7 @@
 #include <grpc/grpc.h>
 #include <grpc/support/thd.h>
 #include <grpc/support/time.h>
+#include <grpc/support/tls.h>
 #include <gtest/gtest.h>
 
 #include "src/proto/grpc/testing/duplicate/echo_duplicate.grpc.pb.h"
@@ -59,6 +60,8 @@ using grpc::testing::EchoRequest;
 using grpc::testing::EchoResponse;
 using std::chrono::system_clock;
 
+GPR_TLS_DECL(g_is_async_end2end_test);
+
 namespace grpc {
 namespace testing {
 
@@ -67,10 +70,12 @@ namespace {
 void* tag(int i) { return (void*)(intptr_t)i; }
 
 #ifdef GPR_POSIX_SOCKET
-static int non_blocking_poll(struct pollfd* pfds, nfds_t nfds,
+static int maybe_assert_non_blocking_poll(struct pollfd* pfds, nfds_t nfds,
                                           int timeout) {
-  /* ignore timeout and always use timeout 0 */
-  return poll(pfds, nfds, 0);
+  if (gpr_tls_get(&g_is_async_end2end_test)) {
+    GPR_ASSERT(timeout == 0);
+  }
+  return poll(pfds, nfds, timeout);
 }
 
 class PollOverride {
@@ -89,7 +94,7 @@ class PollOverride {
 class PollingOverrider : public PollOverride {
  public:
   explicit PollingOverrider(bool allow_blocking)
-      : PollOverride(allow_blocking ? poll : non_blocking_poll) {}
+      : PollOverride(allow_blocking ? poll : maybe_assert_non_blocking_poll) {}
 };
 #else
 class PollingOverrider {
@@ -195,6 +200,8 @@ class AsyncEnd2endTest : public ::testing::TestWithParam<bool> {
     builder.RegisterService(&service_);
     cq_ = builder.AddCompletionQueue();
     server_ = builder.BuildAndStart();
+
+    gpr_tls_set(&g_is_async_end2end_test, 1);
   }
 
   void TearDown() GRPC_OVERRIDE {
@@ -205,6 +212,7 @@ class AsyncEnd2endTest : public ::testing::TestWithParam<bool> {
     while (cq_->Next(&ignored_tag, &ignored_ok))
       ;
     poll_overrider_.reset();
+    gpr_tls_set(&g_is_async_end2end_test, 0);
   }
 
   void ResetStub() {
@@ -1169,6 +1177,9 @@ INSTANTIATE_TEST_CASE_P(AsyncEnd2endServerTryCancel,
 
 int main(int argc, char** argv) {
   grpc_test_init(argc, argv);
+  gpr_tls_init(&g_is_async_end2end_test);
   ::testing::InitGoogleTest(&argc, argv);
-  return RUN_ALL_TESTS();
+  int ret = RUN_ALL_TESTS();
+  gpr_tls_destroy(&g_is_async_end2end_test);
+  return ret;
 }