Add --print_stacktrace_at_api_error.

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 8050833851e76dcf9ebf7ad25252bb842e24aa91..4c73446f0c5f78fd240f766636d228d47a976a6e 100644
--- a/runtime/vm/thread_pool.cc
+++ b/runtime/vm/thread_pool.cc
@@ -447,7 +447,10 @@ void ThreadPool::Worker::Main(uword args) {
   ThreadPool* pool;
 
   // Set the thread's stack_base based on the current stack pointer.
-  os_thread->set_stack_base(Thread::GetCurrentStackPointer());
+  uword current_sp = Thread::GetCurrentStackPointer();
+  if (current_sp > os_thread->stack_base()) {
+    os_thread->set_stack_base(current_sp);
+  }

[siva, 2017/04/13 01:50:18]

Which situation causes the code inside the 'if' statement to be executed?

 
   {
     MonitorLocker ml(&worker->monitor_);