Track async causal stack traces

runtime/vm/thread_registry.h

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_THREAD_REGISTRY_H_
 #define RUNTIME_VM_THREAD_REGISTRY_H_
 
 #include "vm/globals.h"
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
@@ skipping 50 matching lines @@
   Thread* free_list_;    // Free list of Thread objects that can be reused.
 
   // TODO(asiva): Currently we treat a mutator thread as a special thread
   // and always schedule execution of Dart code on the same mutator thread
   // object. The ApiLocalScope has been made thread specific but we still
   // have scenarios where we do a temporary exit of an Isolate with live
   // zones/handles in the API scope :
   // - Dart_RunLoop()
   // - IsolateSaver in Dart_NewNativePort
   // - Isolate spawn (function/uri) under FLAG_i_like_slow_isolate_spawn
+  // Similarly, tracking async_stack_trace requires that we always reschedule
+  // on the same thread.
   // We probably need a mechanism to return to the specific thread only
   // for these specific cases. We should also determine if the embedder
   // should allow exiting an isolate with live state in zones/handles in
   // which case a new API for returning to the specific thread needs to be
   // added.
   Thread* mutator_thread_;
 
   friend class Isolate;
   friend class SafepointHandler;
   DISALLOW_COPY_AND_ASSIGN(ThreadRegistry);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_THREAD_REGISTRY_H_