src: make watchdog async callback a lambda

`Watchdog::Async` features only once for the
async callback, so make it a lambda.

PR-URL: #25945
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/node_watchdog.cc

@@ -39,7 +39,11 @@ Watchdog::Watchdog(v8::Isolate* isolate, uint64_t ms, bool* timed_out)
                "Failed to initialize uv loop.");
   }
 
-  rc = uv_async_init(loop_, &async_, &Watchdog::Async);
+  rc = uv_async_init(loop_, &async_, [](uv_async_t* signal) {
+    Watchdog* w = ContainerOf(&Watchdog::async_, signal);
+    uv_stop(w->loop_);
+  });
+
   CHECK_EQ(0, rc);
 
   rc = uv_timer_init(loop_, &timer_);
@@ -80,13 +84,6 @@ void Watchdog::Run(void* arg) {
   uv_close(reinterpret_cast<uv_handle_t*>(&wd->timer_), nullptr);
 }
 
-
-void Watchdog::Async(uv_async_t* async) {
-  Watchdog* w = ContainerOf(&Watchdog::async_, async);
-  uv_stop(w->loop_);
-}
-
-
 void Watchdog::Timer(uv_timer_t* timer) {
   Watchdog* w = ContainerOf(&Watchdog::timer_, timer);
   *w->timed_out_ = true;

src/node_watchdog.h

@@ -45,7 +45,6 @@ class Watchdog {
 
  private:
   static void Run(void* arg);
-  static void Async(uv_async_t* async);
   static void Timer(uv_timer_t* timer);
 
   v8::Isolate* isolate_;