Revert "Track the 'awaiter return' call stack..."

runtime/vm/scopes.cc

Index: runtime/vm/scopes.cc
diff --git a/runtime/vm/scopes.cc b/runtime/vm/scopes.cc
index e7c04323367039040209ec798b4ba7870dddae1e..75f5d688bf59de6de2765c8cbac70974820850f5 100644
--- a/runtime/vm/scopes.cc
+++ b/runtime/vm/scopes.cc
@@ -264,18 +264,6 @@ static bool IsFilteredIdentifier(const String& str) {
     // Keep :async_op for asynchronous debugging.
     return false;
   }
-  if (str.raw() == Symbols::AsyncCompleter().raw()) {
-    // Keep :async_completer for asynchronous debugging.
-    return false;
-  }
-  if (str.raw() == Symbols::ControllerStream().raw()) {
-    // Keep :controller_stream for asynchronous debugging.
-    return false;
-  }
-  if (str.raw() == Symbols::AwaitJumpVar().raw()) {
-    // Keep :await_jump_var for asynchronous debugging.
-    return false;
-  }
   return str.CharAt(0) == ':';
 }