Helper ast node sequences must not wrongly grab ownership of the enclosing

runtime/vm/ast.h

 // Copyright (c) 2011, 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_H_
 #define VM_AST_H_
 
 #include "vm/allocation.h"
 #include "vm/assert.h"
 #include "vm/growable_array.h"
@@ skipping 189 matching lines @@
 };
 
 
 class SequenceNode : public AstNode {
  public:
   SequenceNode(intptr_t token_index, LocalScope* scope)
     : AstNode(token_index),
       scope_(scope),
       nodes_(4),
       label_(NULL)  {
-    ASSERT(scope_ != NULL);
   }
 
   LocalScope* scope() const { return scope_; }
 
   SourceLabel* label() const { return label_; }
   void set_label(SourceLabel* value) { label_ = value; }
 
   void VisitChildren(AstNodeVisitor* visitor) const;
 
   void Add(AstNode* node) { nodes_.Add(node); }
@@ skipping 1696 matching lines @@
   const LocalVariable& context_var_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(InlinedFinallyNode);
 };
 
 }  // namespace dart
 
 #undef DECLARE_COMMON_NODE_FUNCTIONS
 
 #endif  // VM_AST_H_