Fix scope/context behavior in await transformer.

runtime/vm/ast_transformer.h

 // 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.
 
 #ifndef VM_AST_TRANSFORMER_H_
 #define VM_AST_TRANSFORMER_H_
 
 #include "platform/assert.h"
 #include "vm/ast.h"
 
@@ skipping 51 matching lines @@
 
   AstNode* Transform(AstNode* expr);
 
  private:
   LocalVariable* EnsureCurrentTempVar();
   LocalVariable* AddToPreambleNewTempVar(AstNode* node);
   ArgumentListNode* TransformArguments(ArgumentListNode* node);
   AstNode* LazyTransform(const Token::Kind kind,
                          AstNode* new_left,
                          AstNode* right);
+  LocalScope* NewScope(LocalScope* parent);
 
   void NextTempVar() { temp_cnt_++; }
 
   Isolate* isolate() const { return isolate_; }
 
   SequenceNode* preamble_;
   int32_t temp_cnt_;
   AstNode* result_;
   const Library& library_;
   ParsedFunction* const parsed_function_;
 
   Isolate* isolate_;
 
   DISALLOW_COPY_AND_ASSIGN(AwaitTransformer);
 };
 
 }  // namespace dart
 
 #endif  // VM_AST_TRANSFORMER_H_