Hacky fix for kernel bots

runtime/vm/kernel_to_il.cc

 // Copyright (c) 2016, 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.
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "vm/kernel_to_il.h"
 
@@ skipping 3165 matching lines @@
       VariableDeclaration* variable = named[i];
       body += LoadLocal(LookupVariable(variable));
       body += CheckVariableTypeInCheckedMode(variable);
       body += Drop();
     }
   }
 
   if (FLAG_causal_async_stacks &&
       (dart_function.IsAsyncFunction() || dart_function.IsAsyncGenerator())) {
     LocalScope* scope = parsed_function_->node_sequence()->scope();
-    // :async_stack_trace = _asyncStackTraceHelper();
+    // :async_stack_trace = _asyncStackTraceHelper(:async_op);
     const dart::Library& async_lib =
         dart::Library::Handle(dart::Library::AsyncLibrary());
     const Function& target = Function::ZoneHandle(
         Z,
         async_lib.LookupFunctionAllowPrivate(Symbols::AsyncStackTraceHelper()));
     ASSERT(!target.IsNull());
 
+    // TODO(johnmccutchan): Why does this have the null value?
     LocalVariable* async_op =
-        scope->LookupVariable(Symbols::AsyncOperation(), true);
+        scope->child()->LookupVariable(Symbols::AsyncOperation(), false);
     ASSERT(async_op != NULL);
+    ASSERT(async_op->is_captured());
     body += LoadLocal(async_op);
     body += PushArgument();
     body += StaticCall(TokenPosition::kNoSource, target, 1);
     LocalVariable* async_stack_trace_var =
         scope->LookupVariable(Symbols::AsyncStackTraceVar(), false);
     ASSERT(async_stack_trace_var != NULL);
     body += StoreLocal(TokenPosition::kNoSource, async_stack_trace_var);
     body += Drop();
   }
 
@@ skipping 3249 matching lines @@
     thread->clear_sticky_error();
     return error.raw();
   }
 }
 
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)