Include the awaiter stack trace in the service protocol

runtime/vm/scopes.cc

Index: runtime/vm/scopes.cc
diff --git a/runtime/vm/scopes.cc b/runtime/vm/scopes.cc
index e7c04323367039040209ec798b4ba7870dddae1e..c972b0f7a43c6d4d154102ea66a136146f5739a2 100644
--- a/runtime/vm/scopes.cc
+++ b/runtime/vm/scopes.cc
@@ -276,6 +276,10 @@ static bool IsFilteredIdentifier(const String& str) {
     // Keep :await_jump_var for asynchronous debugging.
     return false;
   }
+  if (str.raw() == Symbols::AsyncStackTraceVar().raw()) {
+    // Keep :async_stack_trace for asynchronous debugging.
+    return false;
+  }
   return str.CharAt(0) == ':';
 }