In background compilation make a copy of Field in order to freeze its state

runtime/vm/ast_transformer.cc

 // Copyright (c) 2014, 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/ast_transformer.h"
 
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/thread.h"
 
@@ skipping 504 matching lines @@
 
 
 void AwaitTransformer::VisitLoadStaticFieldNode(LoadStaticFieldNode* node) {
   result_ = node;
 }
 
 
 void AwaitTransformer::VisitStoreStaticFieldNode(StoreStaticFieldNode* node) {
   AstNode* new_value = Transform(node->value());
   result_ = new(Z) StoreStaticFieldNode(node->token_pos(),
-                                        node->field(),
+                                        *node->field().OriginalAsHandle(Z),

[siva, 2016/02/25 23:38:32]

ditto comment.

[srdjan, 2016/02/26 00:40:42]

Resolved using Field::ZoneHandle

                                         new_value);
 }
 
 
 void AwaitTransformer::VisitLoadIndexedNode(LoadIndexedNode* node) {
   AstNode* new_array = Transform(node->array());
   AstNode* new_index = Transform(node->index_expr());
   LocalVariable* result = AddToPreambleNewTempVar(
       new(Z) LoadIndexedNode(node->token_pos(),
                              new_array,
@@ skipping 60 matching lines @@
 
 
 void AwaitTransformer::VisitThrowNode(ThrowNode* node) {
   AstNode* new_exception = Transform(node->exception());
   result_ = new(Z) ThrowNode(node->token_pos(),
                              new_exception,
                              node->stacktrace());
 }
 
 }  // namespace dart