dart2js: Remove rethrow from the CPS and Tree IRs.

pkg/compiler/lib/src/tree_ir/tree_ir_tracer.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_tracer;
 
 import 'dart:async' show EventSink;
 import '../tracer.dart';
 import 'tree_ir_nodes.dart';
 
@@ skipping 64 matching lines @@
   }
 
   visitReturn(Return node) {
     _addStatement(node);
   }
 
   visitThrow(Throw node) {
     _addStatement(node);
   }
 
-  visitRethrow(Rethrow node) {
-    _addStatement(node);
-  }
-
   visitUnreachable(Unreachable node) {
     _addStatement(node);
   }
 
   visitBreak(Break node) {
     _addStatement(node);
     if (breakTargets.containsKey(node.target)) {
       blocks.last.addEdgeTo(breakTargets[node.target]);
     }
   }
@@ skipping 170 matching lines @@
   }
 
   visitReturn(Return node) {
     printStatement(null, "return ${expr(node.value)}");
   }
 
   visitThrow(Throw node) {
     printStatement(null, "throw ${expr(node.value)}");
   }
 
-  visitRethrow(Rethrow node) {
-    printStatement(null, "rethrow");
-  }
-
   visitUnreachable(Unreachable node) {
     printStatement(null, "unreachable");
   }
 
   visitBreak(Break node) {
     Block block = collector.breakTargets[node.target];
     String name = block != null ? block.name : '<missing label>';
     printStatement(null, "break $name");
   }
 
@@ skipping 333 matching lines @@
       String prefix = v.element == null ? 'v' : '${v.element.name}_';
       while (name == null || _usedNames.contains(name)) {
         name = "$prefix${_counter++}";
       }
       _names[v] = name;
       _usedNames.add(name);
     }
     return name;
   }
 }