Enable await in for and for-in loops.

runtime/vm/flow_graph_builder.cc

 // Copyright (c) 2012, 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/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/class_finalizer.h"
@@ skipping 2097 matching lines @@
     AddInstruction(
         new(I) CheckStackOverflowInstr(node->token_pos(),
                                        owner()->loop_depth()));
   }
 
   if (node->condition() == NULL) {
     // Endless loop, no test.
     Append(for_body);
     exit_ = nested_loop.break_target();  // May be NULL.
   } else {
+    EffectGraphVisitor for_test_preamble(owner());
+    if (node->condition_preamble() != NULL) {
+      node->condition_preamble()->Visit(&for_test_preamble);
+      Append(for_test_preamble);
+    }
+
     TestGraphVisitor for_test(owner(), node->condition()->token_pos());
     node->condition()->Visit(&for_test);
     Append(for_test);
 
     BlockEntryInstr* body_entry = for_test.CreateTrueSuccessor();
     AppendFragment(body_entry, for_body);
 
     if (nested_loop.break_target() == NULL) {
       exit_ = for_test.CreateFalseSuccessor();
     } else {
@@ skipping 2073 matching lines @@
   Report::MessageF(Report::kBailout,
                    Script::Handle(function.script()),
                    function.token_pos(),
                    "FlowGraphBuilder Bailout: %s %s",
                    String::Handle(function.name()).ToCString(),
                    reason);
   UNREACHABLE();
 }
 
 }  // namespace dart