- Fix for issue 25950 (add registration of a thread exit callback)

runtime/vm/thread_pool.cc

Index: runtime/vm/thread_pool.cc
diff --git a/runtime/vm/thread_pool.cc b/runtime/vm/thread_pool.cc
index b281d5c47fb6344392ca24a817418a2d6d9f216f..70bac99675bfd66b65c0e53418dea7ae99caf57d 100644
--- a/runtime/vm/thread_pool.cc
+++ b/runtime/vm/thread_pool.cc
@@ -4,6 +4,7 @@
 
 #include "vm/thread_pool.h"
 
+#include "vm/dart.h"
 #include "vm/flags.h"
 #include "vm/lockers.h"
 
@@ -480,6 +481,12 @@ void ThreadPool::Worker::Main(uword args) {
     // wait for the thread to exit by joining on it in Shutdown().
     delete worker;
   }
+
+  // Call the thread exit hook here to notify the embedder that the
+  // thread pool thread is exiting.
+  if (Dart::thread_exit_callback() != NULL) {
+    (*Dart::thread_exit_callback())();
+  }
 }
 
 }  // namespace dart