dart2js: Remove rethrow from the CPS and Tree IRs.

pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart

 // 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.
 
 library tree_ir.optimization.statement_rewriter;
 
 import 'optimization.dart' show Pass;
 import '../tree_ir_nodes.dart';
 import '../../io/source_information.dart';
 import '../../elements/elements.dart';
@@ skipping 593 matching lines @@
       node.value = visitExpression(node.value);
     }
     return node;
   }
 
   Statement visitThrow(Throw node) {
     node.value = visitExpression(node.value);
     return node;
   }
 
-  Statement visitRethrow(Rethrow node) {
-    return node;
-  }
-
   Statement visitUnreachable(Unreachable node) {
     return node;
   }
 
   Statement visitBreak(Break node) {
     // Redirect through chain of breaks.
     // Note that useCount was accounted for at visitLabeledStatement.
     // Note redirect may return either a Break or Continue statement.
     Jump jump = redirect(node);
     if (jump is Break &&
@@ skipping 727 matching lines @@
   VariableUseCallback callback;
 
   VariableUseVisitor(this.callback);
 
   visitVariableUse(VariableUse use) => callback(use);
 
   static void visit(Expression node, VariableUseCallback callback) {
     new VariableUseVisitor(callback).visitExpression(node);
   }
 }