Remove AbstractVisitor.

dart/lib/compiler/implementation/compile_time_constants.dart

 // 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.
 
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of
  * optional parameters.
  */
 class ConstantHandler extends CompilerTask {
@@ skipping 221 matching lines @@
   Constant getInitialValueFor(VariableElement element) {
     Constant initialValue = initialVariableValues[element];
     if (initialValue === null) {
       compiler.internalError("No initial value for given element",
                              element: element);
     }
     return initialValue;
   }
 }
 
-class CompileTimeConstantEvaluator extends AbstractVisitor {
+class CompileTimeConstantEvaluator extends Visitor {
   bool isEvaluatingConstant;
   final ConstantSystem constantSystem;
   final TreeElements elements;
   final Compiler compiler;
 
   CompileTimeConstantEvaluator(this.constantSystem,
                                this.elements,
                                this.compiler,
                                [bool isConst])
       : this.isEvaluatingConstant = isConst;
@@ skipping 555 matching lines @@
       Constant fieldValue = fieldValues[field];
       if (fieldValue === null) {
         // Use the default value.
         fieldValue = compiler.compileConstant(field);
       }
       jsNewArguments.add(fieldValue);
     });
     return jsNewArguments;
   }
 }