Fix scoping async functions.

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 23 matching lines @@
 //   t_2 = :result_param;
 //   t_3 = foo();
 //   t_4 = t_2.operator+(t_3);
 //
 // and a resulting expression of a load of t_4.
 //
 class AwaitTransformer : public AstNodeVisitor {
  public:
   AwaitTransformer(SequenceNode* preamble,
                    const Library& library,
-                   ParsedFunction* const parsed_function)
-    : preamble_(preamble),
-      temp_cnt_(0),
-      library_(library),
-      parsed_function_(parsed_function),
-      isolate_(Isolate::Current()) {
-    // We later on save the continuation context and modify the jump counter
-    // from within the preamble context (in the FlowGraphBuilder). Look up the
-    // needed variables to get their corresponding aliases.
-    preamble->scope()->LookupVariable(Symbols::AwaitContextVar(), false);
-    preamble->scope()->LookupVariable(Symbols::AwaitJumpVar(), false);
-  }
+                   ParsedFunction* const parsed_function,
+                   LocalScope* function_top);
 
 #define DECLARE_VISIT(BaseName)                                                \
   virtual void Visit##BaseName##Node(BaseName##Node* node);
 
   FOR_EACH_NODE(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
   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* ChainNewScope(LocalScope* parent);
+  LocalVariable* GetVariableInScope(LocalScope* scope, const String& symbol);
 
   void NextTempVar() { temp_cnt_++; }
 
   Isolate* isolate() const { return isolate_; }
 
   SequenceNode* preamble_;
   int32_t temp_cnt_;
   AstNode* result_;
   const Library& library_;
   ParsedFunction* const parsed_function_;
+  LocalScope* function_top_;
 
   Isolate* isolate_;
 
   DISALLOW_COPY_AND_ASSIGN(AwaitTransformer);
 };
 
 }  // namespace dart
 
 #endif  // VM_AST_TRANSFORMER_H_