dart2js cps: Clean up and avoid processing unreachable code.

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 561 matching lines @@
     });
 
     return node;
   }
 
   Expression visitNot(Not node) {
     node.operand = visitExpression(node.operand);
     return node;
   }
 
-  Expression visitFunctionExpression(FunctionExpression node) {
-    new StatementRewriter.nested(this).rewrite(node.definition);
-    return node;
-  }
-
   Statement visitReturn(Return node) {
     node.value = visitExpression(node.value);
     return node;
   }
 
   Statement visitThrow(Throw node) {
     node.value = visitExpression(node.value);
     return node;
   }
 
@@ skipping 652 matching lines @@
   Variable variable;
   bool wasFound = false;
 
   IsVariableUsedVisitor(this.variable);
 
   visitVariableUse(VariableUse node) {
     if (node.variable == variable) {
       wasFound = true;
     }
   }
-
-  visitInnerFunction(FunctionDefinition node) {}
 }
 
 typedef VariableUseCallback(VariableUse use);
 
 class VariableUseVisitor extends RecursiveVisitor {
   VariableUseCallback callback;
 
   VariableUseVisitor(this.callback);
 
   visitVariableUse(VariableUse use) => callback(use);
 
-  visitInnerFunction(FunctionDefinition node) {}
-
   static void visit(Expression node, VariableUseCallback callback) {
     new VariableUseVisitor(callback).visitExpression(node);
   }
 }