RemoveFromGraph on definitions asserts empty use lists.

runtime/vm/intermediate_language.h

 // 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.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 2354 matching lines @@
     if (propagated_type.IsNull()) {
       // Not a typed definition, e.g. access to a VM field.
       return false;
     }
     const bool changed =
         propagated_type_.IsNull() || !propagated_type.Equals(propagated_type_);
     propagated_type_ = propagated_type.raw();
     return changed;
   }
 
+  virtual Instruction* RemoveFromGraph(bool return_previous = true);
+
   UseVal* use_list() { return use_list_; }
   void set_use_list(UseVal* head) {
     ASSERT(head == NULL || head->previous_use() == NULL);
     use_list_ = head;
   }
 
  private:
   intptr_t temp_index_;
   intptr_t ssa_temp_index_;
   // TODO(regis): GrowableArray<const AbstractType*> propagated_types_;
@@ skipping 497 matching lines @@
   const GrowableArray<BlockEntryInstr*>& block_order_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_