Revert "Proper sequencing of _asyncStackTraceHelper in Kernel"

runtime/vm/kernel_binary_flowgraph.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 "vm/kernel_binary_flowgraph.h"
 
 #include "vm/compiler.h"
 #include "vm/longjump.h"
 #include "vm/object_store.h"
 
@@ skipping 3269 matching lines @@
       SkipVariableDeclaration();  // read ith variable.
     }
   } else {
     // Still skip past the parameters.
     SkipListOfVariableDeclarations();  // read list of positionals.
     SkipListOfVariableDeclarations();  // read list of named.
   }
 
   SkipDartType();  // read return type.
 
+  if (FLAG_causal_async_stacks &&
+      (dart_function.IsAsyncFunction() || dart_function.IsAsyncGenerator())) {
+    LocalScope* scope = parsed_function()->node_sequence()->scope();
+    // :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->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();
+  }
+
   bool has_body = ReadTag() == kSomething;  // read first part of body.
 
   if (dart_function.is_native()) {
     body += flow_graph_builder_->NativeFunctionBody(first_parameter_offset,
                                                     dart_function);
   } else if (has_body) {
     if (is_in_builtin_library_toplevel &&
         IsGetMainClosure(dart::String::Handle(Z, dart_function.name()))) {
       body += BuildGetMainClosure();
     } else {
@@ skipping 3810 matching lines @@
     metadata_values.SetAt(i, value);
   }
 
   return metadata_values.raw();
 }
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)