dart2js cps: Clean up and avoid processing unreachable code.

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 446 matching lines @@
   }
 
   String visitNot(Not node) {
     String operand = visitExpression(node.operand);
     if (usesInfixNotation(node.operand)) {
       operand = '($operand)';
     }
     return '!$operand';
   }
 
-  String visitFunctionExpression(FunctionExpression node) {
-    return "function ${node.definition.element.name}";
-  }
-
   String visitGetField(GetField node) {
     String object = visitExpression(node.object);
     String field = node.field.name;
     if (usesInfixNotation(node.object)) {
       object = '($object)';
     }
     return '$object.$field';
   }
 
   String visitSetField(SetField node) {
@@ skipping 133 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;
   }
 }